Add environment file to systemd unit configuration.

Now there is at least one environment variable that controls
synapse server's behaviour: SYNAPSE_CACHE_FACTOR.
So, it makes sense to make systemd unit file to use
environment configuration file that can set this variable's value.

Signed-off-by: Oleg Girko <ol@infoserver.lv>

Add new author

Intern lots of strings

Don't require alias in public room list.

Make get_invites return RoomsForUser

Only cache events in the event cache

Make StateHandler._state_cache only store event_ids.

Rooms now no longer require an alias to be published.

Also, changes the way we pull out state of each room to not require
fetching all state events.

Fix membership count for BulkPushRuleEvaluator

Don't cache events in _state_group_cache

Make stateGroupCache honour CACHE_SIZE_FACTOR

Instead, simply cache the event ids, relying on the event cache to cache
the actual events.

The problem was that while the state groups cache was limited in the
number of groups it could hold, each individual group could consist of
thousands of events.