* An API for user defined agents has been created
- introducing interface ClassPlayer
- implementing AbstractClassPlayer from most of ClassPlayerAgent
- providing MyClassPlayer as an example
- the BitSets used for representing sets of cards have been 'abstracted' info CardSets which can expose Cards
- Card (which are actually integer representing their position in BitSets) shows features
- AbstractClassPlayer also offers access to the environment
- This is documented in INTERFACE.MD

* ClassGraphiSession was a copy of ClassSession with various modifications
- whatever I found to relocate has been relocated in ClassSession
- this involves quite some reorganisation, but seems to work