Possible wee_extension update

[Rich Bell]

I’ve got an extension that can be installed as either a driver or service. Depending on which, the updates to WeeWX configuration is different. Currently I instruct people to set an environment variable to control the install. I’m wondering if passing in an option to wee_extension would make sense. If so, I’d be happy to work on a pull request (with the caveat of no guarantee of how quick)

rich