Linux issues

[gdevic]

Most current issues on Linux are caused by poor Mono implementation. Also, it appears that the newer Mono (ex. 6.8.x) found on Ubuntu 20.04 introduced a host of new issues which were not present in older Mono (ex. 4.6.2) found on Mint 19.1.

Those are:

1. Missing icons in various tree views (Branches, Repos, but not Commits!) in GitForce
2. Missing icons in generic dialogs like Open File
   These two could be related to this Mono bug: OpenFileDialog, buttons icons are broken  mono/mono#17493
   Mono 4.6.2 correctly shows all icons.
3. File association on edit stopped working (Edit Using -> Associated Editor)
   Mono is responsible for opening a file using the default editor on Process.Start() and 4.6.2 was correctly doing it.

Existing related Mono Linux issues are:
4. File selection dialog shows unfriendly list of "HDD (loop..)" references. They do resolve into root folders when clicked, though.
This issue is also present in previous Mono versions. This dialog is supplied by the framework and not by the app.

None of these are going to be fixed in the app.