Toggle 'submitted' class on whats-new-form when posting activity items

This new class will make nice styling effects easier to build into child
themes.

See #4816

Props hnla

git-svn-id: https://buddypress.svn.wordpress.org/trunk@7161 cdf35c40-ae34-48e0-9cc9-0c9da1808c22
Use jQuery.closest() to find form when submitting activity update

Using closest() instead of traversing with parent() makes the JS much more
flexible, as theme authors are free to change how elements are nested without
breaking the JS.

Fixes #4816

Props hnla

git-svn-id: https://buddypress.svn.wordpress.org/trunk@7162 cdf35c40-ae34-48e0-9cc9-0c9da1808c22