smarter path detection of rhino installation folder

[tkmmark]

For those with multiple version of Rhinos installed, or Rhinos installed in odd directories, the current hard-coded _get_ironpython_lib_path_OS does not always work

For instance... my Rhino 6 is installed inside Rhinoceros2.app folder, not Rhinoceros.app. As such, I must edit line 79 and line 124 in the init.py of compas_rhino to get the compas_rhino installation working.

[tomvanmele]

did Rhino change that name or did you? :) because i have Rhinoceros.app and RhinoWIP.app...

[tkmmark]

Not sure how it happened... Probably not... I would have preferred to rename it according to its version number.

[jf---]

@tomvanmele old let's keep weeding stale issues