Tidied up the editor.
Remove stray commit.
Revert changes that broke the memory view.
Added support for .pcheckoff memory-based checkoffs.
Behave better with visible scrollbars.
Don't explode when asked to check off a program with no checkoff.
Added and used a new ModalDialog class.
Merge branch 'master' into editor

Conflicts:
	editor/editor.js
Merge into editor branch, which apparently had changes.
Editor now prompts to save when closing an unsaved file.
The editor now warns before leaving a page with unsaved work.