This includes just the Python "kinetics" examples to start

Sphinx-gallery creates new .rst files alongside existing manually
maintained documentation, and runs the samples in-place, generating
their output files in the source tree. Moving this all to the build
directory lets us keep the repo clean.

This was causing problems with re-importing cantera.with_units.units
while running the samples as part of the sphinx-gallery build

This sidebar usually only had a "get page source" link, which isn't
very useful for autogenerated pages.

Introduce a monkey patch to avoid executing specific examples that
won't run under sphinx-gallery.