This PR does multiple things:
- the kinds are changed from custom objects to a proper enum.Enum class
(including according changes to the cython code and the kind generation scripts)
- all examples and tests are modified to account for the change how to use kinds
(Kind instead of kinds)
- add docstrings to the kind enum values
- add a custom documenter that properly renders enums via autodoc
- extend doxygen setup so that we can write comments as rst (allowing us to copy
the documentation for kinds from the cpp api to the other apis)
This PR adds documentation to the python class Op, Grammar, Result, and for API enums.
Additionally, documentation for isNull functions in the datatype classes is added for the python API, and a small change in the cpp API documentation is introduced.
This PR adds api::Solver::getOptionInfo() that returns information about a single option, including its name, aliases, current and default value and its domain.
