Add error codes to troubleshooting and a page for GenQuery

[alanking]

Addresses irods/irods#6631

I already spent the time on this so I'm putting this up here, but we don't have to use it.

The only thing the issue calls for is the error codes and a page for iquest attrs, so, take what seems good and we'll throw out the rest (which could be all of it)

[korydraughn]

I like it. Once the review comments are handled, this will be ready.

[alanking]

I am also aware of the ability to use or or || in GenQuery, but I am not comfortable documenting it because I don't know that I fully understand how it works. :) Should we include that or just leave it out?

[korydraughn]

Let's include it just for completeness. You can document the syntax and include a very brief statement about it being the equivalent of where CONDITIONS and (ATTRIBUTE = 'V1' or ATTRIBUTE = 'V2').

[alanking]

Okay, I added the || piece. I'll take a look into the order/order_desc thing to see if I can draw any conclusions.

[alanking]

I will squash this soon (no #s) if there are no further comments.

[korydraughn]

The suggestions by @trel seem good. Other than that, the PR is ready in my book.

[korydraughn]

Looks good. Let's squash it.

[alanking]

Squashed.

[korydraughn]

Pound it.

[alanking]

#'d. Mergin.