This change removes the timestamp field from messages and conversations
in favor of multiple semantically named timestamp fields: sent_at,
received_at on messages; active_at on conversations. This requires/lets
us rethink and improve our indexing scheme thusly:
The inbox index on conversations will order entries by the
conversation.active_at property, which should only appear on
conversations destined for the inbox.
The receipt index will use the message.sent_at property, for effecient
lookup of outgoing messages by timestamp, for use in processing delivery
receipts.
The group index on conversation.members is multi-entry, meaning that
looking up any phone number in this index will efficiently yield all
groups the number belongs to.
The conversation index lets us scan messages in a single conversation,
in the order they were received (or the reverse order). It is a compound
index on [conversationId, received_at].
This was used to conditionally render messages in the group style, but
it's actually unnecessary. We can render the same markup in both cases
and change the appearance with css.
Move base64 encoding of attachments to an AttachmentView. This makes
image rendering an asynchronous task so we fire an update event to
indicate to the parent MessageListView that its content has changed
height and it is time to scroll down.
Register the runtime callback at the top level view rather than having
each conversation view register independently.
Also refactors Layout into InboxView.
After a message is saved asynchronsly, fire an event and pass the
message attributes to frontend listeners via the chrome-runtime API.
This behavior is similar to the 'storage' event fired by localStorage.
Getting up and running with IndexedDB was pretty easy, thanks to
backbone. The tricky part was making reads and writes asynchronous.
In that process I did some refactoring on Whisper.Threads, which
has been renamed Conversations for consistency with the view names.
This change also adds the unlimitedStorage permission.
