This removes the 'allocations' table entirely, and cleans up the way we
prune old messages. This should make it easier to summarize each
connection (for usage stats) when it gets deallocated, as well as making
pruning more reliable.
This requires a DB delete/recreate when upgrading. It changes the server
protocol, and app IDs, so clients cannot interoperate with each other
across this change, nor with the server. Flag day for everyone!
Now apps do not share channel IDs, so a lot of usage of app1 will not
cause the wormhole codes for app2 to get longer.
This removes "side" and "msgnum" from the URLs, and puts them in a JSON
request body instead. The server now maintains a simple set of messages
for each channel-id, and isn't responsible for removing duplicates.
The client now fetches all messages, and just ignores everything it sent
itself. This removes the "reflection attack".
Deallocate now returns JSON, for consistency. DB and API use "phase" and
"body" instead of msgnum/message.
This changes the DB schema, so delete the DB before upgrading the server.
