[feature] Add ability to connect to ILO over HTTPS proxy

[John Gooch]

Use case: I manage ILO's for multiple business partners, and we've had them set up proxies to make accessing parts of their internal network, including HP ILO's from from our network, easier.

I looked at the source code for hpilo.py and dependencies, and I didn't see support for using a proxy connection. I only went as far as socket.py

I'm proposing something like the way the requests module supports proxy, by defining a proxy dictionary. Details here - https://2.python-requests.org/en/master/user/advanced/#proxies.