gruntless invenio

Removing grunt from invenio, one dependency at the time.

**todo**:
- [x] bower.json dependencies should be empty.
- [x] updated documentation
- [x] ~~translations~~ #828, #1989
- [ ] inveniosoftware/invenio-demosite#28
- [x] files that where not in bower.json but are still present in some templates:
   - [x] ~~[recline](http://okfnlabs.org/recline/)~~ #1998
   - [x] ~~[mediaelement](http://mediaelementjs.com/)~~ #1999
   - [x] `ui.datepicker.min.js` bibcirculation/templates.py (replaced by jquery-ui.js)
   - [x] ~~`backbone`, `underscore`, `parsley`, `handlebars`, ... bibauthorid/templates.py~~ #2000

Closes #1842 
I should have remove it before ...