[py] Install py modules and OGS_USE_PATH env var for wrapped cli tools
- Install Python modules into install tree (even when not building wheel).
- Introduces
OGS_USE_PATH
environment variable. When setogs
and other cli tools are used from thePATH
when invoked via wrapped cli tools from python.
Related to:
Fixes ogs/tools/ogstools#20 (closed). Therefore also partly resolves ogs/tools/ogstools#24 (closed).