PaloAlto firewall license monitoring

I created this a while back for a customer who wanted to view and alert on license expiry within their PaloAlto firewalls.

It uses the same API key and API connection methods as our core PaloAlto_FW_* LogicModules, and calls the '<request><license><info></info></license></request>' endpoint.

Monitors for days until expiry (or, whether the license is perpetual, or has already expired).

Alert thresholds in this version are as requested by the original customer, at 60 and 30 days remaining, and for "has already expired".

v1.0.0: FGMCN9