CORE GUI should prompt user for "Save Changes?" if user quits before saving

```
What steps will reproduce the problem?
1. Create a new *.imn file
2. Edit the *.imn with the CORE GUI
3. Quit without saving; all edits are lost

What is the expected output? What do you see instead?

Expect CORE to ask user whether they want to save changes
before quitting.

What version of the product are you using? On what operating system?

- CORE 4.4rc1
- Ubuntu 12.04

Please provide any additional information below.

```

Original issue reported on code.google.com by `fltemp...@gmail.com` on 23 Oct 2012 at 4:34

Start with the CORE GUI workflow for creating and editing a new *.imn file, then trace what happens when the window is quit before saving. Reproduce the issue on Ubuntu or an equivalent environment and verify that quitting with unsaved edits prompts whether to save, without losing the edits when saving is chosen.

Written by the indexing model from the issue text.