Pedestal scalings using published data

[jonmaddock]

The DEMO pedestal scaling has been removed from the open source version of PROCESS as it was based on EUROfusion data.

The best we can get to a published version is here.

If we want a scaling based on real published data we could try these papers:
Role of the separatrix density in the pedestal performance in deuterium low triangularity JET-ILW plasmas and comparison with JET-C (26 pages) , and

Pedestal structure, stability and scalings in JET-ILW: the EUROfusion JET-ILW pedestal database (50 pages),
both by Lorenzo Frassinetti.

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Remember also that using such scalings can give perverse results. If, for example, you increase the pedestal density, but you don't change the volume-average density, the code will reduce the central density, which is unphysical. (The central density can even become negative - see #736.)

Note that the behaviour is different with the central temperature, which is given by a completely different formula:

$T_{ped}$ appears with a plus sign at the beginning of the formula, but the sign of the second term depends on the sign of $\gamma$.

[chris-ashe]

Note that the central temperature function has been found to be incorrect as is now replaced by