* Make the Answer button look nice and laid out properly.
* Merge the time and status labels, displaying simply the text
"Calling..." until the call becomes active and then the call time
afterwards.
* Fix info display bar in both the call and main windows so they use a
GtkRevealer and work a lot better.
* Add a "new-call-symbolic" icon for the "Add call" button.
* General tweaks and clean-ups
Closes#55Closes#35
Put the call display in an GtkOverlay and add a dial pad sending DTMF
tones as an overlay. Also make the dial pad overlay be triggered by the
dial pad button.
Add 'mute' and 'dial pad' buttons, drop the 'hold' button, change the
size of the central buttons, make them use icons and drop the now
useless group size.