Rewrite - Githubissues

Full Rewrite of FIRESONG

Luminosity functions, Evolutions are now implemented as classes
Flux / Luminosity conversion directly takes into account z dependence
heavy clean ups and more explicit use of Functions and removed unneeded parts
input output seperated into external file
Tried to comment / document each function
made PEP8 compatible (some lines are still to long)
implemented Theos fluxPDF calculation as additional script
Tested against current base, no change in results visible. Also cross-checkt transient mode for Firesong.py

Please cross-check and see if it is well documented.

icecube / FIRESONG