Version-specific scratchpad overlays.
Scratchpad - editing a script (disable more items) - all

Disable view commands (Run, Inspect, Display) from context menu and toolbar. Disable access keys.
Scratchpad - editing a script (disable more items)

Disable view commands (Run, Inspect, Display) from context menu and toolbar. Disable access keys.
Scratchpad - first running

Not first line.

[Previously editing enhancements]
Create scratchpad-overlay.js from script in the .xul.

Refs #1774
Clean up scratchpad-overlay.js.

Shorter and simpler.

Fixes #1776
Remove getStatsObj from EXPORTED_SYMBOLS.

This shouldn't have been released, it was only exported for temporary debugging.

Fixes #1782