User documentation needs update

[mggr]

The current azgcorr manual is pretty far out of date in several areas. This has caused problems for users that rely on it.

So far, all we've done is refer them to the -help output for detailed usage, as that is definitive.

Bill has apparently updated the manual but it's not yet complete.

We should probably consider asking if we can help him with it as the current situation is bad for users or, alternatively, write our own version (would be better to use Bill's text if possible IMHO).