#1 Resizable buffer

[Jason Wood]

It would be very nice if piave could resize it's
video window on the fly. Some of the benefits :

- It would allow better use of the monitor screen
real estate when run from within Kdenlive.

- Piave could be run in a window, and then be
switched to "full screen" mode for export to video
functionality or similar.

- It gives the user more control over their screen
layout.