Added comments for spontaneous curvature in energy.c and tape

Samo Penic

2017-09-19 e6efc61995516174081e923004477e3ff0853515

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Original written by Dan Kroll in FORTRAN. Code was then largely adapted and commented by Miha Fosnaric-Fosni. Rewritten into C by Samo Penic-Peni, with help of Miha's extensive explanations.