Initial fix for #2479: New post should be displayed on timeline only if it belongs...

Initial fix for #2479: New post should be displayed on timeline only if it belongs there (AJAX post)

Previously we pushed out your latest post into the currently visible timeline regardless of whether it belonged there or not. This could be pretty confusing!

Currently we don't have clearly machine-readable info on the page and returned notice HTML to determine whether it belongs, but we can do a couple checks easily which I've added:
* public timeline (always show)
* 'and friends' timeline (show for your own page only)
* profile timeline (show for your own page only)

Other places that should be added in the future:
* group timelines if it's a group your posting to
* tag timelines if the post contains the tag
* reply & friends timelines for people you've mentioned

Currently those aren't easy since the mention/group target links in the notice HTML are using the canonical form with user or group ID, while the available navigation links we can use to identify the current page use the names.