Option to copy data when export

Sometimes is needed a fast operation that does'nt require video/audio recompress:

- When the user only wants to "render" a selected portion of a video, and the result only needs to be a cut of the original.
- When the user only wants to concatenate some small videos to render a big one (all with the same format & codecs)
- When the user only makes a project to replace the audio track from a video clip.

The export processing without codec renderings makes possible to process videos without loosing quality on each process.

AND A LOT OF THANKS FOR THIS GREAT PROJECT