Joint-ISI dithering: fixed a bug regarding first ISI bin (#396)
Joint-ISI dithering: fixed a bug regarding first ISI bin (#396)

* fixing boundaries of joint-isi
* possible fix of the first-bin-error
* changed values of padding
NeuralEnsemble/elephant,INM-6/elephant,mdenker/elephant,INM-6/elephant,INM-6/elephant,NeuralEnsemble/elephant,mdenker/elephant,NeuralEnsemble/elephant,mdenker/elephant