Splined bespoke plasma profiles and updated poloidal beta

[chrismarsden7]

Hi!

This update focused primarily in jtor.py and involved adding additional profile types. Previously, FreeGS has only been able to constrain BetaP/central pressure and plasma current, for profile parametrised by the (1-alpha_m)^alpha_n shape.

I have added equivalent functions that that pprime and ffprime data as a function for psi_norm. Splines are created from these data and are then used as a replacement for jtorshape in the previous ConstrainBetaPIp etc profiles.

I have then added variations of these for constraining pprime itself instead of BetaP, ffprime instead etc. to give the user the most possible options when it comes to what exactly they want constrained. There is even a profile that will constrain pprime and ffprime themselves (without constraining any other plasma parameters).

Whilst at it, I fixed the definition of beta poloidal which was incorrect, and has now been update in line with the literature - a couple of supporting methods in equilibrium.py were added.

An example, number 17, has been added to demonstrate using the splined profiles.

[chrismarsden7]

Forgot to actually import interp1d - has now been added.

[chrismarsden7]

Need to fix for the number 17 example

[chrismarsden7]

Example 17 fixed and working as intended