Fix bugs and add a few small useful features:

* Fix Schedule view to properly parse schedule output and respond to switching
  back to graph views.
* Add shorcuts for showing edges of selected nodes.
  - 'i' shows all inputs
  - 'o' shows all outputs
  - '1'-'9' shows all nodes nth input where 1 <= n <= 9
  - 'c' shows all control inputs
  - 'e' shows all effect inputs
* Holding the control key down when using a edge-showing shortcut toggles edge
  state rather the just showing.
* 'a' selects all nodes in graph view.
* Node selection is preserved between graph views and Schedule views.
* Holding control key down when using regular expression search shows currently
  hidden nodes that match the regex search.
* Pane expansion buttons now respond to clicks in entire button area.
* Default text in regex search box makes searching more discoverable.

Review-Url: https://codereview.chromium.org/2059193002
Cr-Commit-Position: refs/heads/master@{#36932}