Allow sponsors to location target collections at house priority.
Fix location targeting for sponsors.

Also return 403 responses for invalid location targets, rather than
setting location to None.
Allow all users to view a requested ad.

Previously this was only allowed for sponsors or the owner of the ad.
Don't fire pixels or fetch trackers on requested ads.
default_thing_wrapper: Don't set rowstyle_cls, it will get overwritten.

Builder also calls add_props, which completely overwrites the attribute.