Machine settings

[ChrisHughes]

Adds:

• Machine Settings dialog with known field specialization
• Fixes 3D viewport on MacOS
• Fixes UI contrast issues
• Sets default Jog step & feed rate instead of being left uninitialized
• Fixes some spindle max speed default weirdness
• MacOS CI build config

[Schildkroet]

Thanks for the contribution.
Linux build fails currently:

../src/frmmain_settings.cpp: In member function ‘void frmMain::loadSettings()’:
../src/frmmain_settings.cpp:151:56: error: ambiguous overload for ‘operator=’ (operand types are ‘QStringList’ and ‘<brace-enclosed initializer list>’)
  151 |         jogSteps = {"0.01", "0.1", "1", "5", "10", "50"};

Could you talk a look at it?

[Schildkroet]

I checked the new machine settings. It works for me, but one issue. It says, only changed values are updated, but for me all settings are written. Is this the expected behaviour?