Openpgp security update (V2) (#31)

* Change keyring unlock functionalities

* Add keyring#Lock, keyring#CheckIntegrity, tests

* Update helpers, fix bugs

* Update go.mod with ProtonMail/crypto commit

* Change key management system

* Clear keys from memory + tests

* Create SessionKey with direct encryption for datapackets. Move symmetrickey to password.

* Fix upstream dependencies

* Update module to V2, documentation

* Add linter

* Add v2 folder to .gitignore

* Minor changes to KeyID getters

* Remove old changelog

* Improve docs, remove compilation script

.golangci.yml

@@ -0,0 +1,54 @@
+linters-settings:
+  godox:
+    keywords: # default keywords are TODO, BUG, and FIXME, but we override this by ignoring TODO
+      - BUG
+      - FIXME
+  funlen:
+    lines: 100
+    statements: 80
+
+issues:
+  exclude-use-default: false
+  exclude:
+    - Using the variable on range scope `tt` in function literal
+
+linters:
+  enable:
+    - deadcode          # Finds unused code [fast: true, auto-fix: false]
+    - errcheck          # Errcheck is a program for checking for unchecked errors in go programs. These unchecked errors can be critical bugs in some cases [fast: true, auto-fix: false]
+    - gosimple          # Linter for Go source code that specializes in simplifying a code [fast: true, auto-fix: false]
+    - govet             # Vet examines Go source code and reports suspicious constructs, such as Printf calls whose arguments do not align with the format string [fast: true, auto-fix: false]
+    - ineffassign       # Detects when assignments to existing variables are not used [fast: true, auto-fix: false]
+    - staticcheck       # Staticcheck is a go vet on steroids, applying a ton of static analysis checks [fast: true, auto-fix: false]
+    - structcheck       # Finds unused struct fields [fast: true, auto-fix: false]
+    - typecheck         # Like the front-end of a Go compiler, parses and type-checks Go code [fast: true, auto-fix: false]
+    - unused            # Checks Go code for unused constants, variables, functions and types [fast: false, auto-fix: false]
+    - varcheck          # Finds unused global variables and constants [fast: true, auto-fix: false]
+    - depguard          # Go linter that checks if package imports are in a list of acceptable packages [fast: true, auto-fix: false]
+    - dogsled           # Checks assignments with too many blank identifiers (e.g. x, _, _, _, := f()) [fast: true, auto-fix: false]
+#    - dupl              # Tool for code clone detection [fast: true, auto-fix: false]
+    - funlen            # Tool for detection of long functions [fast: true, auto-fix: false]
+#    - gochecknoglobals  # Checks that no globals are present in Go code [fast: true, auto-fix: false]
+#    - gochecknoinits    # Checks that no init functions are present in Go code [fast: true, auto-fix: false]
+    - goconst           # Finds repeated strings that could be replaced by a constant [fast: true, auto-fix: false]
+    - gocritic          # The most opinionated Go source code linter [fast: true, auto-fix: false]
+    - gocyclo           # Computes and checks the cyclomatic complexity of functions [fast: true, auto-fix: false]
+    - godox             # Tool for detection of FIXME, TODO and other comment keywords [fast: true, auto-fix: false]
+    - gofmt             # Gofmt checks whether code was gofmt-ed. By default this tool runs with -s option to check for code simplification [fast: true, auto-fix: true]
+    - goimports         # Goimports does everything that gofmt does. Additionally it checks unused imports [fast: true, auto-fix: true]
+#    - golint            # Golint differs from gofmt. Gofmt reformats Go source code, whereas golint prints out style mistakes [fast: true, auto-fix: false]
+    - gosec             # Inspects source code for security problems [fast: true, auto-fix: false]
+    - interfacer        # Linter that suggests narrower interface types [fast: true, auto-fix: false]
+    - maligned          # Tool to detect Go structs that would take less memory if their fields were sorted [fast: true, auto-fix: false]
+    - misspell          # Finds commonly misspelled English words in comments [fast: true, auto-fix: true]
+    - nakedret          # Finds naked returns in functions greater than a specified function length [fast: true, auto-fix: false]
+    - prealloc          # Finds slice declarations that could potentially be preallocated [fast: true, auto-fix: false]
+    - scopelint         # Scopelint checks for unpinned variables in go programs [fast: true, auto-fix: false]
+#    - stylecheck        # Stylecheck is a replacement for golint [fast: true, auto-fix: false]
+    - unconvert         # Remove unnecessary type conversions [fast: true, auto-fix: false]
+    - unparam           # Reports unused function parameters [fast: true, auto-fix: false]
+    - whitespace        # Tool for detection of leading and trailing whitespace [fast: true, auto-fix: true]
+
+  disable:
+    - wsl               # Whitespace Linter - Forces you to use empty lines! [fast: true, auto-fix: false]
+    - lll               # Reports long lines [fast: true, auto-fix: false]\