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
Added configuration api endpoint stubs.
Adds a configure method to controller.
Adds plugin type map.
Adds some WIP payloads for endpoints.