Improve help page and add documentation to edit forms

Here's a draft of what this might look like.

• View: Grants this role the ability to view nodes with the term. The role must have access content permission at admin/user/permissions#module-node. Users must have this permission to see nodes with the term listed in Views.
• Update, Delete: Grants this role the ability to edit or delete nodes with the term, respectively. The role must not have edit any [content type] content or delete any [content type] content permissions at admin/user/permissions#module-node if you want to control them here.
• Create: Grants this role the ability to add the term to a node when creating or updating it. This does not give the role the ability to create nodes by itself; the role must have create [content type] content at admin/user/permissions#module-node in order to create new nodes.
• List: Whether this role can see the term listed on node pages and in lists, and whether the user can view the taxonomy/term/x page for the term. This does not control whether the role can see the nodes listed in Views, only the term.

Options for View, Update, and Delete are Allow (A), Ignore (I), and Deny (D). Deny overrides allow. (However, deny cannot revoke grants given by modules other than Taxonomy Access).

For more information and for troubleshooting guidelines, see the help pages and README.txt.

There'd be links above to the core permissions admin, the readme, and the help. I think that covers the top 10 support questions for TAC in as little space as possible.

I'd also add this same text to the d.o docs and the README for consistency.

I updated the documentation at http://drupal.org/node/31601 with the explanations above. I will create a patch to add it to the admin forms.

The attached patch clarifies the help page in several pages and improves its XHTML compliance. It also adds instructions at the bottom of the admin forms (rather than the top, so that experienced users don't have to scroll past them every time).

Patch is rolled at the module directory level; use the -p option.

Tested and works fine.

Marked #358178: Elaborate relation to core node permissions as duplicate.

The patch in #3 needs a slight change; for some reason I used substitution patterns in a couple t() calls that should have been part of the translation. I'll fix this tomorrow.

Also, a line should be added reminding users to check the authenticated user permissions, as specific roles inherit them.

Marked #165848: TAC permissions overriden by core? as duplicate of this for the documentation part. A summary of "gotchas" is in http://drupal.org/node/165848#comment-2669316.

Revised patch. This improves the documentation further. Applied and tested against a clean copy of 6.x-1.x-dev; works fine.

Committed to 6.x-1.x-dev with a slight fix to the url fragments in help page links.