Fix #571: Footer broken on RTD site
Remove stuff that's not needed for the theme
Update copyright

The copyright in the build configuration file shows in the default
footer.
Hide default footer in docs by hiding default copyright

The default footer only consists of the copyright statement, so we
can get rid of the footer by not showing the copyright.

Instead we show a custom footer thanks to @umcsdon.
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
Related to #614 Change resolution for input Video (Test Ver)

Related to #614
- Add more options for Video Passthrough Setting, which will change the output video resolution.
Fix the python format problem.
delete the space in a blank line.
Add the standard scale and improve the way to read the resolution
Improve the code style according to the code review.