Fix #501 Warn user about losing new talk info

When the user switches from one talk to another, exits the talk editor,
or creates a new talk when the currently selected talk has unsaved
changes, a window comes up warning the user that there are unsaved
changes. The options are "Save Changes", "Discard Changes", and
"Continue Editing".

Fix #501
Close #605
Different Recording UI layout; Persistent buttons
Delete empty files on stop
 Icon only buttons; All custom icons; Disable leave recording mode on record
No system icons, use only custom; Removed "Prepare to record" icon
Record button no longer needs to maintain state

Previously, the stop button would look pressed
because the state was needed for operation.
This state is now being maintained by a
separate variable.
Renamed buttons
New button styles
Moved auto-record feature to menu
Added "Leave" button to Auto Record screen
Added shortcut for leaving auto-record (same as entering auto-record)
Using lambda functions instead of creating caller methods/functions