Move the user page to the new sidebar classes.
The user page has been updated to use the new sidebar code for the

profile and group information. This improves the rendering of the

groups, makes the page easier to maintain, and also improves

extensibility.
With this, the existing hooks are now useless, and will be removed in a

future patch.
I've also cleaned up how the two different modes for the sidebar work

(scrolling vs. fit-to-content). A "scrollable" CSS class on the sidebar

puts the sidebar into scrolling mode. The default is now fit-to-content.

Tested the user page with a lot of review requests (scrolling off the

screen) and with no contents. The sidebar always had the right page.
The groups all linked to their correct URLs.
The profile information reflected the viewing user, and not the requesting

user.
Also retested the dashboard views to make sure nothing broke.