This commit adds support for viewing all the details of a card in a
separate widget. The user simply needs to press the Enter key to view
the card. To return to the Kanban board the user needs to press the
Escape key.
Part of apollo/pelican#16
Replace the existing 'move' tview Page with a new board mode called
'Status Selection'. This mode is used to move cards between statuses.
Resolvesapollo/pelican#11
