#660140 by dagmar: Add a raw user name filter so that we can do more filtering purely on the user name.

Major re-organization of handlers. PLEASE NOTE: This drastically affected the Views module API and until modules are updated to match, they will stop working. Efforts have been made to ensure that this won't cause your site to crash, but that's partly up to the individual module as well.

#274360: Add hard path checking to Node from URL and User from URL to get instances where core menu loader functions are not in use.

Exposed filter memory was being trashed by a rewriting validate; also, exposed filters that decided not to participate weren't properly storing that status in session. This fixes both things.

Some refactoring of how handlers are handled, particularly with their default options. This is an unfortunately widespread change and will affect modules utilizing the API.

#262673: users_roles tables was not being joined properly, causing filters and arguments for roles not not always work right.

#259914: Exposed user: name filter broken. This also affected taxonomy, so fixed that at the same time.

Restore missing functionality from Views 1 to node: nid argument; expand node validator to compensate; also give that functionality to user: uid and node revision: vid

Tutorial for creating a "user list" view in the getting started doc, plus some fixes for bugs the tutorial revealed.

Various fixes, including making sure that exposed filter settings pass through to argument links and pager links.