luci-app-mosquitto: import new application

Originally developed and maintained at https://github.com/remakeelectric/owrt_pub_feeds/tree/master/luci-app-mosquitto

Vs the original, this version has been converted to use the luci.mk
style, and has dropped the now obsolete ucitrack entries.

Signed-off-by: Karl Palsson <karlp@etactica.com>