Factored out delivery and withdrawal information. 
Factored out delivery and withdrawal information. 

* added `Delivery` and `Withdrawal` models
* in `GASSupplierOrder`, factored out delivery and withdrawal infos
with ForeignKeys to `Delivery` and `Withdrawal` models
matteo88/gasistafelice,kobe25/gasistafelice,feroda/gasistafelice,befair/gasistafelice,michelesr/gasistafelice,michelesr/gasistafelice,matteo88/gasistafelice,befair/gasistafelice,kobe25/gasistafelice,befair/gasistafelice,feroda/gasistafelice,kobe25/gasistafelice,OrlyMar/gasistafelice,matteo88/gasistafelice,kobe25/gasistafelice,OrlyMar/gasistafelice,matteo88/gasistafelice,feroda/gasistafelice,domthu/gasistafelice,michelesr/gasistafelice,befair/gasistafelice,feroda/gasistafelice,michelesr/gasistafelice,OrlyMar/gasistafelice,OrlyMar/gasistafelice