Improve documentation of `override.*` and `default.*` driver options

[chrcoluk]

Hi

This report has been edited from the original, hence the misleading title.

The documentation for ups.conf has flags that can be applied to the driver as well, can the documentation be updated to reflect this, as this allows the override behaviour of things like battery low state for upsc.

[clepple]

(Note that project maintainers don't get notifications when posts are edited. I'll take a guess at a new issue title; let me know if this isn't the intent of your request.)

Can you describe a little more about the parts of the documentation you are referring to? As a user, how did you go about looking up the options you needed to change?

I'd like to avoid duplicating information in the source tree, but I can see an argument for somehow including common options like override.* and default.* in an AsciiDoc file fragment that gets included in each driver man page (likely pulling in the contents of docs/man/nutupsdrv.txt, and part of the nut.conf man page).