Not possible to install both doublecmd-gtk and doublecmd-qt from the repository

[Горбешко Богдан <bodqhrohro@gmail.com>]

They are representing the same virtual package `doublecmd` and marked to 
conflict with it. I need both for plugin debugging so need to install 
one of them from the tarball. I think it is better to allow installing 
both packages and choose the default one with update-alternatives.