added Schechter CDF and generator
added Schechter CDF and generator

jcesardasilva/agpy,ufoym/agpy,jcesardasilva/agpy,Leotrinos/agpy,tectronics/agpy,tectronics/agpy,Leotrinos/agpy,Leotrinos/agpy,jcesardasilva/agpy,tectronics/agpy,jcesardasilva/agpy,ufoym/agpy,Leotrinos/agpy,ufoym/agpy,tectronics/agpy,ufoym/agpy