CMake: Use $ORIGIN as the RUNPATH for proper resolve of local Coin bu…

…ilds.

add PIVY_Python_SITEARCH install destination

PyObject_CallObject -> PyObject_CallObject

increase version to 0.6.8

Correct Python install directory to be arch specific

Binary (i.e. non-pure) python modules should be installed to an
arch specific directory.
Instead of doing this manually, use the Python_SITEARCH variable
provided by the new FindPython module, available since CMake 3.12.

gh-actions: add conda-forge channel

graphics: small fixes for interaction marker

Release 0.6.5

garphics: fix renamed function

workaround for beveled text