Disable automatic switch for power adapter but not battery

[MrSimmo]

Macos combines the "automatic switching" setting for both battery and power adapter.

Would it be great if gswitch could add an option to monitor whether a power adapter is plugged in and if so disable switching and trigger discreet graphics.

So end result could be:

1. If running on battery, permit dynamic switching
2. If power is plugged in, switch to discreet gpu

Cheers

[CodySchrank]

Duplicate #73