Merge branch 'python-modules' into docs-mw

Merge branch 'python-modules' into docs-mw

scripts/lib was always a bit of an awkward place for Python libraries; give
them a proper home under tools/lib/python.  Put the modules from
tools/docs/lib there for good measure.

The second patch ties them into a single package namespace.  It would be
more aesthetically pleasing to add a kernel layer, so we could say:

  from kernel.kdoc import kdoc_parser

...and have the kernel-specific stuff clearly marked, but that means adding
an empty directory in the hierarchy, which isn't as pleasing.

There are some other "Python library" directories hidden in the kernel
tree; we may eventually want to encourage them to move as well.