implements send contact request page

This patch comprehends the ui of sending contact request and
the logic behind it

The ui is a new page on the stacked widget of callwidget
it contains a text field displaying the RingID of the contact
you want to request and another for a textual help,
there is also a text entry for future text added to contact request
payloads.

Change-Id: I592f74fefa125d6e8cd576f9a49fbd74581cf4c9
Reviewed-by: Anthony Léonard <anthony.leonard@savoirfairelinux.com>