Add the ability to generate background parameters within subsection of spectrum

[eadkins333]

This would enable the phase of an etalon to change across the scan. While other parameters are constant. This needs to be done without breaking up the spectrum into multiple input spectrum.

[eadkins333]

Added this functionality and an additional definition that allows you to impose constraints across the segments for each baseline parameter (ie can force the baseline parameters to be constant across the entire spectrum, but the etalon phase is individual to each segment).

[eadkins333]

closed - 9/4/2019