File dialog doesn't capture and process all keys

[PropGit]

Problem:
New file dialog let's Tab and Shift+Tab key events pass through to the editor; changing the code unexpectedly.

Also, Ctrl+S passes through, and probably many others.

Solution:
When a modal dialog is displayed, all key combinations should be captured and processed with respect to that context, muting (nullifying) any key combinations that do not have a specific intended use in that context (of that dialog).

[PropGit]

This is related to issue #105.