Revert "Publicize: Fix the ability to mark posts as not publicizable with wpas_submit_post? filter."

This reverts commit 2beb14cce962d53a05df0f655f5db47d5fdbaad3.

This changeset was leading to issues where users couldn't publicize posts that were done from any UI other than the web interface.
Merge pull request #368 from Automattic/ui-tweaks

Updated module descriptions & icons added to JP homepage
Add icons to modules page

Icons added in rows on modules page.