CMake (Python Installation) Fixes, master branch (2020.05.07.)

These changes are meant to fix the build errors that showed up last night because of !32540 (merged).

As discussed in !32540 (comment 3432479), the problem came from packages using atlas_install_python_modules( python/*.py ), even though they didn't have any python files in them. So the removal of those calls is the primary intent here.

But while I was modifying the packages, I couldn't resist doing "general cleanups" in them as well. 😛 Since every one of them had problems in the dependency declarations of the libraries/executables that they are building.

Note that it's not impossible that the CI would fail on this, as the removals of the atlas_depends_on_subdirs(...) calls may reveal some further build configuration errors in our code...