propelorm.github.com-310 Fix those gigantic tabs

removed empty css files
added override css file which can be used to override different style behaviours
decreased size of jquery ui tabs

fixes #310
Update jQuery to 1.11.2
Make configuration tabs fit with the site's style

These tabs used to be styled according to the default style-sheet
provided by jQuery UI. They are now stylized like the rest of the site
so they fit better with the design.
Fix configuration tabs display

Since we are using a multi-column layout, the floating elements inside
the tab container make the latter to lose its height so the element are
displayed after the left-floating element (here the navigation menu).

Solution found at http://stackoverflow.com/a/7476799/2663959.
Remove a closing slash to be consistent
Merge pull request #337 from propelorm/configuration-tabs

Improve configuration tab's style