Enable virtual selections in Viewer.

This initializes the Session, SessionView,
and SessionController, without yet enabling
editing, so that cursor movements and therefore
virtual selections work.

Hide the caret and handle.
Merge pull request #333 from adityab/virtual-selections-viewer

Enable Virtual Selections in Viewer
Add ctrl+arrow per-word cursor movement
Merge pull request #316 from tradiaz/master

Add ctrl+arrow per-word cursor movement
Only re-render the selection overlay once per batch of requests

Also, decrease the maximum latency between a render request and when the
update is performed to be 0ms. The previous value of 200ms was quite
noticeable when indenting or unindenting paragraphs.
Merge pull request #329 from peitschie/selection-render-perf

Only re-render the selection overlay once per batch of requests
Add tooltip support for hyperlink