Pyscipopt

Added
- add evaluation of `Expr` in `Solution`.

Added
- add more SCIP functions: `getNSols`, `createPartialSol`

Fixed
- consistent handling of filenames for reading/writing
- fix error when no SCIPOPTDIR env var is set on Windows

Added
- add more SCIP functions: `getNTotalNodes`, `getNIntVars`, `getNBinVars`

Fixed
- `getTransformedVar` now uses `SCIPgetTransformedVar` instead of `SCIPtransformVar` which captures the variable

Added
- add parameter genericnames to Model.writeProblem() to allow for generic variable and constraint names

Fixed
- strip quotes from SCIPOPTDIR path variable that might confuse Windows systems

Added
- allow creation of implicit integer variables
- make some more SCIP functionality available

Fixed
- fix reference counters for Python constraints

Added
- expose even more SCIP functionality in `scip.pxd`

Changed
- `Model.from_ptr` and `Model.to_ptr` use a `PyCapsule` to exchange the SCIP pointer
rather than an integer.
- mark getDualMultiplier() as deprecated, only getDualSolLinear() is supposed to be used to get duals of constraints

Removed
* removed `__div__` from Expr and GenExpr to make it compatible with cython 0.29.20