Equilibrium.psi_n function not returning correct values

[Matej Tomes]

Equilibrium._psi_lcfs wrongly identified in Equilibrium.find_extremes

I discovered this issue by using Equilibrium.psi_n function which returns wrong values.

[Lukáš Kripner]

Equilibrium.__findextremes__() done more robust. Waiting for function self.in_first_wall for better recognition of lcfs.
(672923e)

[Matej Tomes]

in_first_wall function inside the utils/surfaces.py

[Lukáš Kripner]

Should be resolved with #10