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This also removes outdated filespec paths in the python3 package; these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>