Correct app icons

[Blaadick]

It would be great if application icons were selected from the .desktop file, if there is one.
If the name of the process and the .desktop file match, or the names can be contained within each other, then we draw the icon specified in the .desktop file.

Some examples:

Endfield.desktop            <-> Endfield
Arknights: Endfield.desktop <-> Endfield
Endfield.desktop            <-> ArknightsEndfield

For reliability, can be added a configuration file in which you can link process names to icons (but this is a questionable idea).

[H3rmt]

This was implemented to prevent desktop files that specify icons by path from preventing icons from gtk icon themes to be overridden.

I think a config option to configure which one should be preferred could be added