Add CLI flags for custom update lengths

[esfalsa]

This PR adds support for the -maj and -min CLI flags to specify custom lengths. This exposes the same functionality as is currently available in interactive mode.

[AavHRF]

I'm not quite confident that we want to add those flags back. If I recall correctly, we specifically removed the -maj flag in the 2.0 release due to a change in how we handled time calculations. -min makes sense though.

[esfalsa]

Hmm, do you remember what exactly the issue was? The -maj flag as I've implemented it should function the same as the existing functionality for manually specifying an update length, so I figured it would work the same way with respect to time calculations, but I can check the code again.

[AavHRF]

Hmm, do you remember what exactly the issue was? The -maj flag as I've implemented it should function the same as the existing functionality for manually specifying an update length, so I figured it would work the same way with respect to time calculations, but I can check the code again.

I don't remember, unfortunately. Upon testing, however, there seems to be no issue so perhaps I'm confusing this with a change I made in the beta branch. As long as nobody else on the development team is opposed to this change I will merge it into master.

[khronion]

Changes merged. Thank you @esfalsa!