Optimization of category tree JS for older browsers like IE7

git-svn-id: http://svn.montala.net/svn/resourcespace@4350 c08608d7-6e46-0410-86ca-f2a6f1370df5
Added default button to be triggered when user hits enter in form. Fixes previous behaviour in upload form leading to resetting the template.

git-svn-id: http://svn.montala.net/svn/resourcespace@4351 c08608d7-6e46-0410-86ca-f2a6f1370df5