Change titles on File Chooser dialogs

Change titles on File Chooser dialogs

Some prompts have been removed, as redundant

File names ending in .dr~ are shown as normal diagrams, but are "locked"

Logic of Compare function changed; moved to Edit high-level menu

Added Edit/Clear Compare Indicators function (also removes "ghosts")

Create Image also moved to Edit high-level menu

Removed compare 'ghost' function

Removed arrow compare