* Automatically display the overlay when the card details is opened
(previously we waited for the mouse to enter the card details panel)
* Improve the design of the minicards badges
* Change the minicard background when it is hovered or selected
* Removes unimplemented features links from the UI
* Fix the board canvas position when the sidebar is open (was hidden
behind)
Fixes#215
New features:
- select all filtered cards
- assign or unassign a member to selected cards
- archive selected cards
This commit also fix the card sort indexes calculation when a multi-
selection is drag-dropped.
The UI and the internal APIs are still rough around the edges but the
feature is basically working. You can now select multiple cards and
move them together or (un|)assign them a label.