PR feedback

Ensure we only persist an event once at a time

It turns out that it's more useful to return a null device display name (and
let clients decide how to handle it: eg, falling back to device_id) than using
a constant string like "unknown device".

* Factor out some of the code shared between the different sytest jenkins scripts

* Exclude jenkins from the MANIFEST

* Fix dendron build

* Missing new line

* Poke jenkins

* Export the PORT_BASE and PORT_COUNT

* Poke jenkins

Refactor the e2e query handler to separate out the local query, and then make
the federation handler use it.

Fix response cache

Cache federation state responses

Split out the federation reading portions into a separate. 

Fix adding emails on registration

Ignore AlreadyCalled errors on timer cancel

Synapse was not adding email addresses to accounts registered with an email address, due to too many different variables called 'result'. Rename both of them. Also remove the defer.returnValue() with no params because that's not a thing.

Forbid non-ASes from registering users whose names begin with '_'

Handle the case of missing auth events when joining a room

Create separate methods for getting messages to push

for the email and http pushers rather than trying to make a single
method that will work with their conflicting requirements.

The http pusher needs to get the messages in ascending stream order, and
doesn't want to miss a message.

The email pusher needs to get the messages in descending timestamp order,
and doesn't mind if it misses messages.

Comment get_unread_push_actions_for_user_in_range function