Fix mainwindow titles: do not prepend ourselves the appname

Summary:
The appname is appended by the platform (integration) usually,
so that only results in duplication.

Also fix code to now show the map in the title on start.

Reviewers: rahn, nienhueser, #marble

Reviewed By: nienhueser, #marble

Differential Revision: https://phabricator.kde.org/D2088