Allows users to save multiple topic and personal message drafts,
allowing more flexibility around content creation.
The "New Topic" button will now always start a fresh topic. Drafts can
be resumed from the drafts dropdown menu or using the "My Drafts" link
in the sidebar.
Since drafts require a unique `draft_key` and `user_id` combination, we
have updated the format of the draft key for both topics and personal
messages. They will now have a prefix like "new_topic_" or
"new_message_" with the timestamp of when the composer was first opened
appended.
c64b5d6d7a