* Refactor into a python module format
-Updates import statements to be absolute vs implicitly relative
-Uses import syntax that minimizes the need to update references in code
and/or reformat affected lines (e.g. `import gapi.directory` becomes `from gam.gapi import directory as
gapi_directory`)
-Adds a `__main__.py` such that the module can be executed on its own
using standard `python3 -m gam` syntax
-Replaces __main__ import hack with module import
-Updates the GAM path to be the module's parent dir
* Add gam.py to /src for backwards compatibility
A stub that calls gam.__main__.main() to be used by users who are not
with the syntax of calling a module implementation. It should also
provide immediate backwards-compatibility with existing scripts with
references to this file.
* Move build tools back to the main dir and out of the package
* Fix pylint errors
* Update build spec to use new package format
Incorporates @jay0lee's patch from
https://github.com/jay0lee/GAM/pull/1165#issuecomment-618430828
