Document python dependency processing (Wheels, requirements.txt, .py files)

[isc-eneil]

The current documentation is too minimal to be useful (https://github.com/intersystems/ipm/wiki/03.-IPM-Manifest-(module.xml)#pythonwheel and mention of -export-python-deps flag in https://github.com/intersystems/ipm/wiki/02.-CLI-commands#package).

Updated documentation should include:

• explanation of -export-python-deps flag behavior under the hood during package and its consequences on install
• how PythonWheel resources and requirements.txt interacts at build- and deployment-time in the case that 1. there are overlapping python wheels in module.xml and requirements.txt 2. install happens offline 3. install happens online
• how PythonWheel resources are affected by the -export-python-deps flag at package/publish
• a warning against using PythonWheel resources unless there is a very specific reason why completely static Python files are required
• how .py files that are not dependencies but rather part of a package should be included

[isc-dchui]

Added documentation to the wiki on page 2 and page 3.