Py-spec

The calculation of the Hessian has been included as published in the following two articles:
* [A. Kumar et al "Nature of ideal MHD instabilities as described by multi-region relaxed MHD" (2022)](https://doi.org/10.1088/1361-6587/ac53ee)
* [K. Aleynikova et al "Model for current drive induced crash cycles in W7-X" (2021)](https://doi.org/10.1088/1741-4326/ac2ab9)

SPEC is now equipped with cmake and a python wrapper.

The integration with [SIMSOPT](https://github.com/hiddenSymmetries/simsopt) is completed. Example application here: https://doi.org/10.1063/5.0061665

This release implements the numerically well-behaved Zernike basis functions in the centermost volume as well as a host of other improvements to speed and accuracy.

For more information, please see pull request 111

The updated numerical scheme makes the analysis routines (Matlab and Python) incompatible with the output of previous versions of SPEC.

This release enables the use of the _Lconstraint=3_ option, allowing the prescription of toroidal current profiles. This new constraint is compatible with free-boundary SPEC.

Examples
* [InputFiles/TestCases/G1V02L3Fi.001.sp](https://github.com/PrincetonUniversity/SPEC/blob/master/InputFiles/TestCases/G1V02L3Fi.001.sp)
* [InputFiles/TestCases/G2V32L3Fi.001.sp](https://github.com/PrincetonUniversity/SPEC/blob/master/InputFiles/TestCases/G2V32L3Fi.001.sp)
* [InputFiles/TestCases/G3V08L3Fr.001.sp](https://github.com/PrincetonUniversity/SPEC/blob/master/InputFiles/TestCases/G3V08L3Fr.001.sp)

Merge discussion
* Initial merge, without force gradient capability 75
* Force gradient merge 105

This is the version of SPEC used in the [Free Boundary verification paper](https://doi.org/10.1088/1361-6587/ab9a61).

- Free boundary calculations can now be performed by specifying Lfreebound=1 in the input file.
Example input file is [/TestCases/G3V08L1Fr.001.sp](https://github.com/PrincetonUniversity/SPEC/blob/master/InputFiles/TestCases/G3V08L1Fr.001.sp).

- python diagnostics have been significantly expanded.

Details of this specific commit to master: 81
Fixes and implements the discussions detailed in issue 70

Details can be found at 68 and 78 .