python: Rework filespec install script

python: Rework filespec install script

* Support wildcards in install (`+`) paths

* Add fourth parameter to set directory permissions

  If file permissions are given (third parameter), these will now apply
  to files only.

* Add non-recursive set permissions command (`==`)

* Be more strict about filespec format

  Blank lines and lines starting with `#` will be ignored. Other errors
  (unknown command, missing path parameter, etc.) will cause the script
  to exit.

* Be more strict about ensuring paths exist for all commands

* Avoid spawning subshells

This also removes outdated filespec paths in the python3 package; these
paths delete files that are no longer present.

Signed-off-by: Jeffery To <jeffery.to@gmail.com>