Rewrite non-bonded interactions as script interface objects

[jhossbach]

Fixes #4555 and fixes #4569

Description of changes:

• rewrite non-bonded interactions as script interface objects
  • convert Cython file interaction.pyx to Python file interaction.py
  • 1600 lines of Cython code were removed
• bugfix: the set_params() method now raises an error if required arguments are not provided
  • scripts may silently break when a potential is set and later updated in a way that is affected by the bug described in Non-bonded interactions set_params() is broken #4569
• new feature: possibility to deactivate/reset non-bonded interactions
• reduce code duplication in the script interface of bonded interactions

[reinaual]

why do we need a swap here? Probably a move-assignment would be more expressive

[jngrad]

I just looked it up and apparently, a swap was the only way to do a cheap move for std::vector back in C++03. I'll change it to a std::move.

[reinaual]

Have we ever tested the python abstract base class to work together with the ScriptInterface? Probably a lot of the methods would be perfect candidates for @abc.abstractmethod

[jngrad]

Well, it wasn't used before because everything was in Cython, and abstract classes don't work out-of-the-box in Cython:

Error compiling Cython file:
------------------------------------------------------------
...

import abc
cdef class HydrodynamicInteraction(FluidActor, metaclass=abc.ABCMeta):
                                                                    ^
------------------------------------------------------------
/work/jgrad/es/src/python/espressomd/lb.pyx:172:69: C classes cannot take keyword bases.

or

Error compiling Cython file:
------------------------------------------------------------
...

import abc
cdef class FluidActor(abc.ABC):
                        ^
------------------------------------------------------------
/work/jgrad/es/src/python/espressomd/lb.pyx:34:25: First base of 'FluidActor' is not an extension type

The usual workaround was to declare a python abstract class and use it to register the cdef class to make it abstract, which is less elegant and error-prone. Now that the module is in Python, we can use ABC metaclasses.