Dolphin Services: Launch Deb/Rpm archives with QDesktopServices

Summary:
When you are inside the services store and you choose to install a deb/rpm package
they open in the default application (mostlikely a package installer utility like discover).

PS: I have written some ideas/questions, maybe you can comment on them :-) ?

Test Plan:
Tests still pass, try out what was described in the summary.
A product which has a deb/rpm package is for example: `Jetbrains Dolphin Plugin`

Reviewers: #dolphin, elvisangelaccio, ngraham, aspotashev

Subscribers: kfm-devel

Tags: #dolphin

Differential Revision: https://phabricator.kde.org/D28795