Package new PDF.js version: v1.0.907

These changes come from the generic build
of PDF.js v1.0.907, with zero changes.

(I'll re-apply our changesin the next few commits.)
Remove unused 1M sample PDF
PDF.js: re-add our 2-liner viewer customizations
Add CC icons to the icon font
Add CC0 licensing information to the editor
socket: Unexport clientID

This isn't used anywhere else, so simplify the interface of Socket by
inlining a call to get the client ID.
socket: Simplify clientID generation

It's not clear to me why we were using this rather complicated method of
generating a UUID. Suffice to say that simply calling uuid.v4() has much
the same effect.
streamer: Add new streamer service

This commit adds a streamer service that abstracts interaction with the
streamer websocket.
Install and configure the streamer
Replace socket with streamer

Replaces direct use of the websocket with use of the streamer service
introduced in the previous commit.
(whitespace) long lines and injection alignment
Merge pull request #1797 from hypothesis/realtime-cleanup

Frontend realtime cleanup
Remove unused injection in AppController
Switch to ws4py

Since pyramid_sockjs seems pretty unmaintained, having fallen behind
gevent-websocket quite a bit, and there don't seem to be any actively
maintained pyramid websocket integration libraries, switch to using
ws4py directly.

This change drops support for non-native websockets. As a result, we
have to do our own JSON decoding of the messages.

We also switch to a `gevent.pywsgi` based worker of our own. This
worker combines the gevent_pywsgi worker from Gunicorn with the
gevent helpers from ws4py that cleanly shutdown sockets on server
termination.
Move h.auth -> h.account on frontend
Merge pull request #1798 from hypothesis/rename-auth-account

Move h.auth -> h.account on frontend
Update Annotator

... to b8c75146 (typed-packaging branch)

Fixes the shortlink problem with the Document plugin for #1760.

(Also brings in some dead code removal)
Merge pull request #1742 from hypothesis/ws4py

Switch to ws4py
Merge pull request #1795 from hypothesis/CC0-awareness-revision

Add message about CC0 License to Editor (revision)
Fill reply permissions

Privacy directive doesn't fill the permissions if the annotation has
already have them and the replies permissions were not filled, only
the reading permissions

Before that the privacy directive detected that other way.

Fix #1759