ffmpeg command and switch support

[DeusExMachina]

After reviewing Visual Hub, I felt that it would be worth while, and a trivial hack, to add support for adding ffmpeg command line commands and switches, perhaps as a text input field in the options tab. This would allow those who need it to fine tune settings in a more precise and advanced way.

[major]

Thank you for the suggestion, I add it to the to-do list.

[DeusExMachina]

Thanks!
As an additional suggestion, perhaps a was to save these command/switch "presets" by name, so you can load them up again later.