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.

Add wrapper Matlab class that provides cleaner more useful interface to the
matlab.engine.  The engine itself is held as a global variable, so that it
doesn't need to be passed around for multiple invocations.

clarify PRFixed to be bool and True by default

Error is:

  jobs:test:cache:key config cannot contain the "/" character

Updates to materials parameters for new thermal noise estimate, and SRM and
PD params.

 https://dcc.ligo.org/LIGO-T1800044

no functional change

Functions now expect separate (freq, psd) numpy array args

Use IFO name

closes #6