Recorded videos are subtly broken

Expected behavior: If I press record and then hit stop 10 minutes later, I get a 10 minute long video. Actual behavior: The recorded video can be much "shorter", because it has an incorrect frame rate and runs faster.

Related issues: #7 and #4

• If the desired frame rate (e.g. 25fps) can not be achieved, the frames are written as if they were recorded at the desired frame rate.

• This results in a video that appears sped up and shorter.

• If the videos are supposed to be tracked again later, e.g. entity speeds are going to be incorrect.

• This might never get fixed, but maybe we could at least add a warning

• We have to make sure that the new BioTracker deals with this in a better way (e.g. even just repeating previous frames until a new one is available would be better)