[WIP] Moving templates to external bundle

### What is this PR?

This PR will introduce two major changes:

 1. It will move (at least) all views templates to an external Bundle. This should permit us to have something more flexible on enhancements (we could continue to fix core bundle - the parser - will some improvements on templates might be done, ...). Not only templates will be moved through this PR: some logic and core concepts will be also moved to the "Template" Bundle
 2. Taking advantage of rewriting templates to move to [AdminLTE template](http://almsaeedstudio.com/AdminLTE/). 


### Projected key steps

Not sure (need to start developments) what this will bring us, but here is what I imagined for now:
 * [ ] v1: moving to AdminLTE without special additional feature
 * [ ] v2: automatically generating _basic menu_ from generators
 * [ ] v3: including Widgets?
 * [ ] v4: whatever you can imagine :)


### Some questions

 * I still don't know for now if we should also move Actions templates out of the _core bundle_. So the _core bundle_ will mainly manage all parsing part and filters and forms (at least PHP part). 
 Sub-question: if we also move Actions templates, should we move them into another Bundle then the Views one or in the same?
   * **Advantages** about moving actions out of the Core: we can imagine to be able to create "Rest" generator tomorrow based on something already existing. **Drawbacks** maybe to much complicated for developers.. and for us to implement :)
    * **Advantages** about moving actions templates to the same bundle as views: I think views and actions (except in a Rest logic) are "hardly" linked... (not really convinced myself). Creating new views/actions should be simplier than if Actions are in the Core. **Drawbacks**: maybe to much complicated for developers
    * **Advantages** about keeping Actions templates into the _Core_ bundle: creating new templates will be easiest. Just based on some conventions (files names, files locations, ...). **Drawbacks**: less flexibility?





_I had some other questions but totally forget them... Let's update the description after some discussions_