We re-implement the usual key handling by overriding the key press
handler, emulating the according steps but leaving out the
validation that normally rejects certain combinations.
Single key hotkeys work unless an entry is focussed, in which case
the entry receives the input, and Control+Tab works as well.
The shortcuts extension is adjusted to accept any hotkeys.
Extensions used to look for the menu and append items manually.
In order to show Tools in the Compact menu a proper signal
is needed.
Adblock, Shortcuts and Toolbar Editor are ported to the new API.
