Change default theme to KritaDarker? @ settings_table.h

[MorrowShore]

Change default theme to KritaDarker? @ settings_table.h

[askmeaboutlo0m]

Krita Darker looks bad on 2 of 4 screens I have available. On those, the black is so dark that it makes it hard to look at the UI. Krita Dark looks okay on every screen, so it's safer as a default.

I think a more sensible solution is #1207, letting people pick between dark, darker and bright to start with.

Regardless of that, this implementation is not the correct way to change the default color scheme, it would also change it for everyone that currently has it set to Krita Dark.