Do not version external libraries

[lenybernard]

Instead of having a large number of potential unused libraries in each project we setup alertify, I suggest to use front system (like bower, npm, yarn) to manage front libraries such as toastr, notiejs, pushjs...

Doing this will be less "automagic" while every library won't be already in the projet's assets and we won't be able to load dynamically with assetic/injector-bundle.

Some reactions ?