Hide a couple other bits of Articles UI based on the ShowArticlesMenu right
Allow SeeCustomField and ModifyCustomField rights at the Class level

The code already supports checking the context object (here, the Class),
and the context objects are set in RT::Class->ArticleCustomFields.
Support this orthogonal manner of granting rights, which is many times
superior to attempting to set them on every CF individually.
Merge branch '4.2/article-ui-and-cf-rights'