First crack at #486.

Major changes:
-View\Body collapsed to View
-Navigation\Link and collapsed to Navigation
-View\Head and View\Foot collapsed to View\Layout
-New View\Assets package
-Item\File changed to File or Item as appropriate
Update docblocks for Records.
Add primary and sidebar wrappers.
Fix styles for adding elements to item types.
Fix #495, use set_name from element query.

Avoids an extremely large number of additional queries for the same
element set data, just to get the name over and over again.
Correct files/show hierarchy.
Remove ORDER BY from find() queries, fix #496.
Do a single query to get collection names, fix #497.
Restore strip_formatting to collection dropdown.
Trust in the existence of the sessions table, fix #498.
Remove some stuff from default files/show, see #494.
Strip HTML from DC Title for file display title.

Fix #490.
Give contributors change-type permissions. Fix #499.
Make Omeka_Db_Select_PublicPermissions really look at the current user.

I'm hesitant about this commit, since it seems odd that we haven't hit this before. Then again, it only came up while testing the combo of UserProfiles and GuestUser

It looks like the situation of having an owner column, and acl with showSelfNotPublic hasn't come up before? (Or at least hasn't been noticed and reported?)

In any case, this rectified a mysql 'not data in prepared statement error' in the combo of UserProfiles and GuestUser. The $select was coming out with the expected OR clause, but no current user id. So far as I can tell, this won't affect the previous behavior, but wanted to be verbose here because it seems. . . curious. And I could always be missing something or causing some unwanted behavior I hadn't thought about.
oops make that _currentUser property in previous commit protected
Join instead of subquerying for item advanced search.

See #54.
Move content-type setting to controller plugin.

This tries harder to avoid any duplicate setting of the content-type
header, which breaks fastcgi setups.
Account for REDIRECT_ prefix on env vars.

This seems to occur for some FastCGI setups.
Correct borders on error pages and reorder prefixed styles.
Reorder prefixed styles. Fix #504.