240 config vars

[senorprogrammer]

Before this change, all module API keys and sensitive configuration had to be done via ENV vars, which sucks for lots of reasons, chief among them:

• Configuration in multiple places
• Not very easy to remove from the machine
• Leaky, anything else running has access to them
• Blocks support for multiple instances of the same module

This change supports sensitive configuration in the config.yml file. If the necessary value cannot be found there, then it falls back to looking for an ENV var.

Example implementation:

func (widget *Widget) loadAPICredentials() {
   widget.APIKey = wtf.Config.UString(
     "wtf.mods.weather.apiKey",
     os.Getenv("WTF_OWM_API_KEY"),
   )
 }