Cpmpy

* get_core() work around bug in upstream ortools

* still learning the right release flow, this is a stable release

Major
* Reworked solver interface so that it is near-identical to model interface
* Or-tools interface allows unsat core extraction!
* Add MARCO MUS enumerate as example of unsat core extraction usage
* variables now take a name= argument for variable name (easier debugging)

Enhancements
* Added more examples: bibd, npuzzle
* Added 'table' global constraint
* Added support for time\_limit when calling solve()
* Added more tests on the flattening
* Add solution hints to ortools interface
* Improved documentation

Bugfixes
* multiple fixes and improvements in ortools interface
* fix module (thanks HakanK)
* various bugfixes

* still learning the right release flow

Major

* Or-tools is now the default backend

Enhancements
* A new `flat normal form` with `flatten_model` transformation
* Generic global constraint decompositions
* Adding more examples
* Documentation improvements.
* Multiple bug fixes related to the integration of OR-Tools