Implemented thumbnails and edit option for Media files (partially)


* Now you can edit an image or video via their respective tabs.
1) Thumbnails are visible for both of them.
2) Click on 'Thumbnails' can directly give you the access(view/play) to the media resource.
3) Click on 'View details' can give you the edit facility.

* Files modified:
1) videoDashboard.py - 'newgroup' replaced with 'groupid' in video_edit() and video_detail() functions.
2) file.html - Few urls modified in anchor tags of thumbnails and view details respectively.

* For the tab containing All media resources view, these functionalities are going to be implemented very soon.