- cellIntervalToSlice more flexible

static calcMass and calcInertia functions are now available for all geometries

[API]: changed body mapping functions: removed most of them, added mapping-decider function, accomodated changes to test cases, added new mapping test case

[API]: changed pe coupling mapping functions interfaces, added new mapping functions, adapted test cases and benchmarks

 lbmpy boundary handling works on pure flag fields, geometry setup
 classes could only set up boundary handling, not pure flag fields.