Use function from R. Schilling CQG 14 1997.  Particularly needed for longer
arms.

better titles, calc Total difference, and show max fractional error in plots
and in log, and other log cleanup

also clean up docstrings.

Improves readbility.  use translation for MATLAB purposes.

Infrastructure is obviously where it really belongs.  This also allows us
to almost eliminate the need for the Constants struct on our side.

This is mostly used for MATLAB translation, but is useful for a couple of
other things as well (R_earth for instance).

These two functions were basically identical except for the material
used for the test mass stage, and a hacky reduction of the spring
constant for silicon.

suspQuad is modified to support different materials for the test mass
stage, and a hacky switch is added to adjust the spring constant.
suspBQuad is now just a wrapper around suspQuad specifying that the
test mass material is silicon instead of silica (there is definitely a
better way to do this, by e.g. specifying the fiber material in the
Stages struct list).

don't need to be defined inside of the suspQuad function

move this out of noise package, since it's not actually directly a noise
calculation.  no functional change.

The hashes are stored in the pickeled MATLAB results, and uses them to check
if new results need to be calculated based on changes to IFO or gwinc data.

BeamRadius no longer needs to be provided.

Also remove unused/redundant SpotSizes function.

ifo.Suspension.Type now accepts string for suspension calc func, e.g. 'Quad'
for 'suspQuad' calc.

this is already handled in precomp

The output is intended to be identical to that of pygwinc.Struct.to_txt(),
useful for direct comparison.

Assumes the IFOModel is given as function in .m script, and use Matlab
engine interface to execute and load.