code cleanup in multiple files

Last changes were merged quickly without strict code-review
as it was needed to integrate them promptly.
Related modifications:
 * callwidget.cpp: Removed unnecessary line feed
 * callwidget.{cpp,ui}: Renamed “contactRequestView” to
   “contactRequestPage” for consistency
 * contactrequestwidget.cpp: Refactoring of a too-long line
 * sendcontactrequestwidget.{cpp,ui}: Better placeholders

Moreover, contactrequestwidget.{cpp,ui} were missing the GPL
header and copyrights' years are now updated to 2017 in every
files.

Change-Id: Id52f340fc62340df6cf5bda8d782fefc732beabe