0.1.0-alpha: LIBILS-904. Removed custom user-installable plugins, refactor

As part of this commit, I removed the ability for users to
install custom plugins. There is now a pre-set list.

I also refactored the names of the scripts/commands so that
they don't include 'kubernetes' any more - this is now a more
generalizable docker image.

https://umd-dit.atlassian.net/browse/LIBILS-904