better naming for displays with duplicate names
Merge pull request #21 from gboudreau/screen-control

Remember preferred screens, when user selects one from the menu.
Merge branch 'screen-control' of github.com:felixhageloh/uebersicht into screen-control
Small improvements and fixes.

Using a constant instead of hard coded number for the max number of
screens.
Making sure some vars are initialized to nil and not garbage.
actually initializing max_displays might be a good idea