Expand on time-based filtering of annotations

[marcverhagen]

The Mmif class has a useful method get_annotations_between_time, but it only works for time points and time frames.

There is value in expanding this to all annotations in a MMIF file, which would let you created a MMIF file with only those annotation for some time segment.

There is danger here, because that MMIF file would actually not be the MMIF file that you would get by running the apps in the pipeline using the specifications from the view metadata.

There is a somewhat lame effort to do this in https://github.com/clamsproject/mmif-summarizer, but that is still in its infancy.