ExternalEditors: Remove direct dependency on qmake

Change-Id: I3f7193c43fcb0b02e3621fc03b08962b534f441e
Reviewed-by: Eike Ziller <eike.ziller@digia.com>
Git: Remove unused functions

Change-Id: I279dcf1ee1c1fe16d3a1fd866af4f9cc4a8c9070
Reviewed-by: Tobias Hunger <tobias.hunger@digia.com>