global: grunt changes and bootstrap upgrade

* maintainable gruntfile
* tasks run in parallel
* copy files that actually changed
* clean up code
* performance issues
* added licence headers
* added path option for custom path
* upgraded bootstrap to 3.1.1
* upgraded jquery to 2.1.0
* rollback typeahead to previous version
* css fixes for bootstrap 3.1.1

Some changes that have to do with Grunt and dependencies. Grunt tasks now run in parallel (if we want to add more in the future it will be more helpful), tasks take care only of the files that are actually changed (try to run grunt twice), refactored code, upgraded bootstrap and jQuery, fixed CSS issues that broke the search bar and rolled back the version of typeahead not to produce the known error until it is fixed. 

Notes for the new installation: 
$ rm -rf node_modules
$ rm -rf bower_components
$ npm install
$ bower install
$ grunt           # default path now points to '../../var/invenio.base-instance/static/'
(or $ grunt --path='custom/path')