#5 calculate playback time

[glenneroo]

Images will inevitably end up in a video, therefore it would be useful without having to do a pre-render test to calculate the playback time of the video.

Example: 1000 images @ 24fps = 00:41:15

Ideas:
- configurable FPS (24/25/30/custom)
- ? proportional output e.g. for 1 minute (configurable?) of footage where 1 photo every 3 seconds, 20 photos needed.

[glenneroo]