Label: Improve Project Label (Tag)

* Rename Tag to Label.
* Improve UI to edit Project Label.
    * Add scrollbar to view window and make edit window
      auto-resizable(#156).
    * Allow users to input category and name each separately(#157).
    * Show License and Language even if they have no label(#155).
    * Make the Edit button togglable.
    * Add appropriate auto-focus on the input box.

길다보니 뭔가 실수를 한 데가 있을 것만 같고...

![project-label](https://f.cloud.github.com/assets/1129852/635052/670ab33e-d236-11e2-9eff-6057883d0598.png)