Add GUI to manage group settings

[Motrotz]

A simple GUI to create/delete modify the cycling groups, keybindings, and to change the client order would be a great feature. I'm tracking this as an issue to collect ideas on how to design this.

[Motrotz]

I probably want the gui to be split in 3 parts.

1. global setting management
2. group management.
3. quick client switching.

1 and 2 will be tracked here, for 3. I’ll create a separate issue eventually.

Global settings can be kept really small (currently this is only the Enable/disable switching toggle key)
The group management window is where most of the work needs to be done. It should probably have 2 columns, on the left the group list (add/rename/reorder/delete group functionality), and the right column has the groups settings like cycle keys, auto-add and auto-hide true/false toggles, and a list of all character names that are part of this group, ordered the way they are cycled through.