add alternative orientation options

[AberDerBart]

It would be helpful to have the option to rotate the display by 90, 180 or 270 degrees. This way, it can easily be used in different orientations

[daschr]

I'll implement it this weekend.

[AberDerBart]

I already have a draft here, I'll clean it up and send a PR this afternoon

[AberDerBart]

see #18