Support multiple inputs in the same source folder

[sharwell]

This simplifies the use of VAP for experimenting on inputs coming from recordings that are split across many files in the same folder. By specifying sample*.mp4 as the input, it will use sample.mp4, sample2.mp4, sample3.mp4, etc. The user is expected to ensure that the input video resolution and lines configuration are consistent across all inputs matching the pattern.

[ycshu086]

That's a useful feature. Minor: I'd suggest we include video file name into the name of output images to better debug the results. Currently frameID increases monotonically across video files.

[sharwell]

Yes, I think that would help. It wasn't a problem in my experiment because each frame has a timestamp, but I'll think about a way to handle cases that don't.