Added Bootstrap3 compatibility

Hi,

I started using the project with bootstrap 3 and I had mainly problems with the icons and the modals (add link and add image modals).
So, I did the necessary changes (in the minified and non-minified js and in the .css and .less versions) to make all that compatible with bootstrap 3.

Thanks for all the contributors on that project and I hope that my modifications will help the people using bootstrap 3.