Support more options that came with mosquitto 1.4
Use more built in functions to make script simpler to read and easier to
extend.

Signed-off-by: Karl Palsson <karlp@remake.is>

This is actively maintained, and will continue to be maintained.

Upstream development versions of the package is available at
https://github.com/remakeelectric/owrt_pub_feeds

Signed-off-by: Karl Palsson <karlp@remake.is>