Merged from internal
Merge remote-tracking branch 'upstream/master'
made changed according to Andrew Sacamano's comments
changed mode to enum according to Cory Hardman's comments
Merge pull request #11 from darylseah/master

Add K2Exception and i18n framework
Merge pull request #9 from jmaheswaran/master

Added Key, KeyVersion, SymmetricKey, AESKeyVersion, AESKeyVersionTest, AESKeyVersionBuilder, KeyVersionBuilder
Add basic K2 storage system implementation.

- All exceptions.
- Storage driver interfaces
- Internal K2 interface (K2Storage/Store)
- I18n strings