Add window.storage to the background page, which loads all data from the
'items' store in indexeddb, caching them in memory for synchronous
access, then override textsecure storage to use that in memory store.
Storing multiple sessions in a single indexeddb record is prone to
clobbering data due to races between requests to update multiple device
sessions for the same number, since you have to read the current state
of the device->session map and update it. Splitting the records up makes
it so that those updates can be made in parallel. Selecting all the
sessions for a given number can still be done efficiently thanks to
indexeddb range queries.
* Session records are now opaque strings, so treat them that way:
- no more cross checking identity key and session records
- Move hasOpenSession to axolotl wrapper
- Remote registration ids must be fetched async'ly via protocol wrapper
* Implement async AxolotlStore using textsecure.storage
* Add some db stores and move prekeys and signed keys to indexeddb
* Add storage tests
* Rename identityKey storage key from libaxolotl25519KeyidentityKey to
simply identityKey, since it's no longer hardcoded in libaxolotl
* Rework registration and key-generation, keeping logic in libtextsecure
and rendering in options.js.
* Remove key_worker since workers are handled at the libaxolotl level
now
