add generic widgets for some interface

[karlwessel]

This does three things:

1. Implement a widget for IStoppable interfaces
2. implement a widget for the coordinate interfaces ILatLon, IRaDec and IAzAlt.
3. implement a generic widget that can provide gui elements for any module that implements one or more of the above interfaces

This allows to have a ILatLon telescope, like the solar telescope of pyobs-tiptilt that is stoppable without having to define a new interface for those.