Move all dust rendering to its own function

No more 'dust.render' and ugly error handlers inside the callbacks.
Make calendar fonts larger
Fix small typo in Gruntfile.js
Load dustjs-helpers

Old dust.js included them, but this new version requires you to install a
separate component.
Replace jQuery UI blocks with Bootstrap panels

Also restyled the 'Add new calendar' button
Add some space between sidebar blocks
Improve event tooltip performance

Instead of generating a qTip for every event on render time, creates a
single tooltip div that will be shown when clicking on an event.
Hide tooltip after clicking on the same event

To make this work we now add the event start value to the event id, so
recurrent events don't do strange things when clicking on top of them.
Keep event popup controlled by qTip

After several tests, seems that the more consistent behaviour implies not
managing the tooltip by hand.

This implies that double clicking on an event makes the popup reappear on the
event, but we will eventually find a better solution.
Remove 'click' from hide events for tooltips

Sorry, I left it there and shouldn't be. Clicking on the popup made it
hide again.