This adds what I think needs to be done to support categories for flags
but we will see if that works. It also forces the scripts to use python2
since they blow up under python3 which is becoming the default python on
many linux systems.
Small fix to app_test as well so it conforms to the new Flag interface.
This makes sorting flags and other sections consistent with how most
command line tools function, by placing both flags `-A` and `-a` before
a flag `-B`.
plus breaking out "setup" portion of `App.Run` into its own method, cleaning up
some bits of the help templates, and allowing for runtime opt-in of displaying
template errors to stderr.
