Enhanced submission system

- Using "Ladda" buttons, with progress bar embedded in them (see them
live here : http://lab.hakim.se/ladda)
- The submission API now works like this :
1. Uploads into a temp directory
2. Checks if a file with the same name exists
3. If it doesn't, puts the uploaded file in the /packs directory
Corrected tabs
Merge pull request #4 from perfaram/master

Enhanced submission system