Add .DS_Store to .gitignore

Because Mac.
Update Annotator to 6623b2c2 (typed-packaging branch)
Handle an init race condition

... when the bucket bar is being updated
before the document access strategy becomes
available. (This sometimes happens when using
PDF.js in the Chrome extension.)
Update PDF plugin

... to cfac672e (typed-packaging branch).

Fixes #1788.
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
Revert "Add .DS_Store to .gitignore"

This reverts commit 3c5952ddacbfd883ce9f0ea0a2f317a47670de39.

Per feedback from @aron
https://github.com/hypothesis/h/commit/3c5952ddacbfd883ce9f0ea0a2f317a47670de39#commitcomment-8916616
Set elasticsearch requirement higher

Plugin listing support (which we use as of
244130c925d66efd2cf84fe972d452ad9cd5c313)
was added in elasticsearch 1.1.0.
Stripping plugin names after the split

Otherwise it was failing due to a trailing space
after `analysis-icu`
Update Elasticsearch Version

I also included specific instructions for getting elasticsearch to start automatically when the system is booted.
whitespace
Link to install instructions for ICU Analysis plugin
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.