Partial UI Overhaul
- moves the history to its own widget (still doing nothing, though…)
- adds a dial pad overlay to the call display, triggered by its dial pad buthon and sending DTMF tones
- uses a new "new call" widget which handles just that and not the DTMF tones
- displays calls in a secondary window rather than in a the main window
- fix the window's title from Calls to Calls
This makes the UI way closer to the final design!