Cleanup on code and add small Javadoc updates:
1. Update Javadoc to specify the return object in MasterClient#addCheckpoint
2. Fix code alignment
3. Remove // TODO Auto-generated method stub
4. Fix spacing in swith-cases statements in MasterInfo class
5. Fix type comment in DataServerMessage
Revert indent switch-case statements to follow code guidelines.
Remove core/src/main/java/tachyon/hadoop/HdfsFileOutputStream.java per discussion in Tachyon groups
Remove unused exception throws
Remove unneeded return statement
Update Javadoc to remove unthrow Exception
Update Javadoc for MasterInfo#writeImage
Merge pull request #307 from hsaputra/simple_cleanup_master_code_1

Cleanup on unused code, comments, and small Javadoc updates