fixed milestone's unique constraint mapping
Merge pull request #7 from keesun/HIVE-40
add dropdown UI component
fix member role label CSS
fix hive.FileDownloader legacy compatible code
adapt for coding convention
add ui.FindUser

apply ui.Dropdown, ui.FindUser on project.Member
change UI component name
fix search button style
apply ui.FindUser on issue list
fix dropdown for vcs select
fix author-avatar CSS (32x32 overflow hidden)
project: Add Tagging feature.

While getting tags:
* Return 406 if the client cannot accept appcation/json.

While tagging:
* Return the tag if that is tagged newly.
* Create new tag if no tag matches the given name.
* Do nothing if that has been tagged already.

While untagging:
* Respond 404 if no tag matches the given id.
* Delete the tag if there is no project tagged by that.