Updating of protos.

- Switched to saner filenames (discovered java_outer_classname).
- Changed string type to enum Type.
- Extension numbers are now 10000 + <enum type number> (convention).
- Removed IV from AES proto.
- Add skeleton for Key proto.
Add KeyVersionInfo annotation.

- For annotating KeyVersions with (1) the proto type
  and (2) the compiled proto class.
- KeyVersion class now automagically sets the key version type
  when building the data proto and registers the required
  proto extensions when reading the data proto.
- Updated AES and HMAC key versions to use the annotation.

- (Also removed IV proto persistence from AESKeyVersion.)
Add @Documented to StoreDriverInfo annotation.

- Makes the annotation show up in the Javadoc of driver implementations.
- Same thing was added to KeyVersionInfo.
Add unit tests for KeyVersion-proto save/load.
Fix comments on unit tests.
Expand range of HMAC types in proto.
Re-index proto enum values.

- No more skips in numbering.
- Comment at top of enum provides next number.
- Updated AES and HMAC key version extension numbers
  to reflect new type values.
Merge pull request #23 from darylseah/master

Updates to Protos and addition of KeyVersionInfo annotation.