Start to change keyCapture logic with modifiers

Most important change in its API: keyCapture.onKeyPressed now takes a
real letter as string - the conversion to a keyCode is done inside the
service.
Use new keyCapture syntax in sidepanel directive
Define more keyCaptures for token selection
Use new keyCapture syntax in contextMenu
Remove dependency to keyCapture in token
Refactor bindClick() in token directive
Remove obsolete code in keyCapture
Make keyboard token selectors configurable
Add Vimium compatible keyboard conf to staging2
Revert change of moving key-capture directive

Configuration is not a problem - the conf file is accessed through a
function anyway, calling it is therefore lazy and always at the right
time.
Remove obsolete specs for keyCapture service
Add spec for new keyCapture modifier handling