Split out prerequisite validation from creation. Distinguish system prereqs from application prereqs. Support URL autodetection to eliminate requirement to edit file as part of setup. Reviewed-on: https://gitea.subcultureofone.org/greg/tkr/pulls/58 Co-authored-by: Greg Sarjeant <greg@subcultureofone.org> Co-committed-by: Greg Sarjeant <greg@subcultureofone.org>