Change register/available to POST (from GET)

Don't update event cache hit ratio from get_joined_users

Cache check to see if device exists

Cache one time key counts

Otherwise the hit ration of plain get_events gets completely skewed by
calls to get_joined_users* functions.

Revert speed up push

This reverts commit ab37bef8.

This reverts commit ad8b3169.

This reverts commit 421fdf74.

Always mark remotes as up if we receive a signed request from them

	Handle exceptions thrown in handling remote device list updates

Rewrite SimpleHttpClient.request to include timeouts 

Make get_joined_users faster

Fixes #2191

Optimise caches for single key

Add cache for get_current_hosts_in_room

Revert "Prefill state caches"