remove all-error-codes.md

[edwardhartnett]

Fixes #2333.
Part of #2329
Fixes #2186.
Fixes #891

This PR includes PRs #2330 and #2332 and #2384 and should be merged after them (or instead of them).

In this PR I remove all-error-codes.md. These codes are already documented in netcdf.h.

@WardF you probably want to get these documentation fixes in before the 4.9.0 release.

(Also adding netcdf_filter.h to doxygen build.)

[edwardhartnett]

I will take down the pre-cursor PRs, since this PR contains all my documentation changes for 4.9.0...

[WardF]

We've received a lot of questions in the wake of the v4.9.0 release along the lines of 'where did the error code table go'. While they are indeed documented in netcdf.h, they are not presented in the end-user easy-to-read table format they were previously, so I'll be reversing that part of this change (after ensuring it's at parity with the current state of things).