Centralize the logic for macOS install locations
Centralize the logic for macOS install locations

This was previously fairly scattered, and not complete. Borrowed
liberally from Avogadro's build system code.

Signed-off-by: Marcus D. Hanwell <cf7042e2e8eee958b5bcde1ae2cbefef82efc184@kitware.com>

OpenChemistry/tomviz,OpenChemistry/tomviz,OpenChemistry/tomviz,OpenChemistry/tomviz