Added config override feature.

Allows for changing default config values when testing.
None of these are kept for release, so accidental changes
to the main config shouldn't happen anymore.
Fixed 'flicker' effect on dup file view

When the dup view was updated several times a second,
it would cause the flicker effect.
Fixed by only doing updates if model data has changed. This
also prevents doing expensive model updates when nothing has
changed.
Brought back the duplicate file toolbar buttons

They were nixed until functionality could be refactored.
Brought back view and delete functionality

Also added event functionality for status updates