Apply Singleton. Unit Tests.
Update "retrieve" command.
Merge remote-tracking branch 'origin/parser/Victor' into logic/wenhao
Fix integration bugs with Result constructor
Merge branch 'controller/sharon' into logic/wenhao
Merge remote-tracking branch 'origin/parser/Victor' into logic/wenhao
Merge remote-tracking branch 'origin/db/sean' into logic/wenhao
Merge branch 'master' into logic/wenhao
Add documentation for Filter and Handler
Get the Logic agree with database apis
Merge remote-tracking branch 'origin/db/sean' into logic/wenhao
Fix minor bugs with database api
Definition of the database configuration files
Use DBConnector as an interface to the actual connector for abstraction purposes
Allow the creation of entries to the database
Allow updates to entries
Allow all entries to be retrieved
Allow the entry to be deleted
Remove extra information
Updated description