As suggested in #604 there might be some language unnecessary redundancy, for
instance between 'es' (Spanish) and 'es-ES' (Spain's Spanish), but we'll figure
that out during the release candidate phase.
* Implement visibility choice on board creation;
* Rework the board header bar. Remove links to un-implemented
features;
* Implement a board star counter (visible if the board have >2 stars);
* Define a new icon (a thin cross) to close elements;
* Remove $(document).on('mouseover') event handlers that were
basically fired hundreds of times for nothing, we now define a proper
Tracker dependency to execute jquery-ui plugin initialization only
when something has changed;
* Bug fixes related to list scrolling.
