mockup split into core package and collection of patterns

Main reason for this split is that anybody developing nes pattern can only
depend on minimal set of tools that are needed.

- create mockup-core package which will include: pattern registry, base
  pattern, docs app.
- mockup-core parts should be tested
- new design and code for docs app (Bootstrap+Backbone+ReactJS)
- update all bower and npm dependencies to latest
- simplify Gruntfile.js
Merge pull request #249 from plone/mockup-core-split

mockup split into core package and collection of patterns