This requires the psutil module, and is still opt-in based on the report_stats
config option.

Add Cache-Control headers to all JSON APIs

404 correctly on missing paths via NoResource

fixes https://github.com/matrix-org/synapse/issues/2043 and https://github.com/matrix-org/synapse/issues/2029

Use .iter* to avoid copies in StateHandler

It is especially important that sync requests don't get cached, as if a
sync returns the same token given then the client will call sync with
the same parameters again. If the previous response was cached it will
get reused, resulting in the client tight looping making the same
request and never making any progress.

In general, clients will expect to get up to date data when requesting
APIs, and so its safer to do a blanket no cache policy than only
whitelisting APIs that we know will break things if they get cached.

Fix replication after switch to simplejson

rearrange ordering of releases to match chronology

Turns out that simplejson serialises namedtuple's as dictionaries rather
than tuples by default.

bump version

Fix bug where state cache used lots of memory

The state cache bases its size on the sum of the size of entries. The
size of the entry is calculated once on insertion, so it is important
that the size of entries does not change.

The DictionaryCache modified the entries size, which caused the state
cache to incorrectly think it was smaller than it actually was.

CONTRIBUTING.rst: fix CI info

Update purge_history_api.rst

Doc: Make the event_creator routes regex a code block