Switch all mark-read ops to new API using story_hash.
Refactor result codes for SyncService into enums. Remove deleteFeed from SyncService in preference to standard API call.
Refactor sync service task types to use enums.
Merge pull request #367 from ojiikun/master

Android: Mark Read by Hash, Refactoring, Bugfixes
Removing debugging.
Merge branch 'master' into offline

# By ojiikun
# Via Samuel Clay (1) and ojiikun (1)
* master:
  Refactor sync service task types to use enums.
  Refactor result codes for SyncService into enums. Remove deleteFeed from SyncService in preference to standard API call.
  Switch all mark-read ops to new API using story_hash.