Add gradle build file and git ignores.
Add K2Exception super-class.
Add i18n message support framework.
Fixed small issue in i18n Messages init.
Correct copyright formatting.
Remove redundant link to i18n guide.
Revise i18n framework.

- Rename from Messages to K2Strings to avoid confusion
  with K2 protocol messages.
- Add K2Context with ref to K2Strings.
- Refactored K2Strings to be more testable (no more static).
- Added new language-agnostic unit test.
- Fixed some readability issues.
Merge remote-tracking branch 'upstream/master'
Remove trivial K2Exception test.
Merge pull request #11 from darylseah/master

Add K2Exception and i18n framework