Merge pull request #628 from AlexanderDzhoganov/master

Small fix so we don't crash on an invalid AutoStartInstance
Shows the exception's message

Shows the exception's message during a generic "can't connect to the
repo" error.
Merge pull request #629 from Ippo343/master

Shows the exception's message
Testcase for the fix in 37a33
Merge pull request #635 from RichardLake/Testcase37a33

Testcase for the fix in 37a33
Run scan before install or update.

Otherwise it is possible to get into a inconsistent state.
For example if an auto detected dependency is removed.
Closes #381
CmdLine upgrade checks for auto detected mods.
Raise a nice error message instead of a null pointer exception.
Close #605
Remove default -force-opengl on Windows.
Can cause issues such as #630.
Merge pull request #637 from RichardLake/ForceGL

Remove default -force-opengl on Windows.
Fix spurious windows.forms reference.
It was coming from the existence of a GUIMod extension method in a namespace with a using system.windows.forms.
Merge pull request #636 from RichardLake/Issue605

CmdLine: Run scan before install/update, better msg on autoinstalled mods.