Add native compatibility for Fritz lightcurve data

[tylerbarna]

Feature Summary
Given the close ties this project has with Fritz, it would be useful for local instances of NMMA to have a more straightforward method of ingesting Fritz lightcurve data.

Usage / behavior
There's 2 ways this could be approached: either at the time lightcurve-analysis is called, NMMA could check if the lightcurve file provided was in the format expected by NMMA, and, if not, convert it to a .dat or .json format that is compatible with NMMA.

Alternatively, we could have a separate function for doing file conversions.

Alternative Solutions
This would still be useful even if the above is implemented, but a page in the documentation detailing the expected format of lightcurves for NMMA analysis would be beneficial to users.

Implementation details
@bfhealy has already implemented this feature as part of the NMMA Fritz API, which can be seen here. This conversion code can be integrated into NMMA in one of the ways outlined above.