Added first draft of DF backend interface spec.
Added first draft of DF backend interface spec.

linearregression/otrs,StCyr/otrs,eliasp/otrs,PortgasDAce/otrs,nilei/otrs,PortgasDAce/otrs,PortgasDAce/otrs,s7design/otrs,nilei/otrs,vlascoder/otrs,linearregression/otrs,eliasp/otrs,capeit-tto/otrs,rudy500/otrs,brandonshults01/otrs,thorsteneckel/otrs,brandonshults01/otrs,xhoy/otrs,oiami/otrs,StCyr/otrs,MBRG/otrs,MBRG/otrs,nilei/otrs,s7design/otrs,brandonshults01/otrs,noritnk/otrs,mbeijen/otrs-1,crythias/otrs,PortgasDAce/otrs,thorsteneckel/otrs,thorsteneckel/otrs,mburggraf/otrs,moritz/otrs,s7design/otrs,vlascoder/otrs,noritnk/otrs,linearregression/otrs,eliasp/otrs,oiami/otrs,StCyr/otrs,s7design/otrs,brandonshults01/otrs,muehlbauer/otrs,StCyr/otrs,moritz/otrs,muehlbauer/otrs,mburggraf/otrs,rudy500/otrs,xhoy/otrs,nilei/otrs,nilei/otrs,thorsteneckel/otrs,mbeijen/otrs-1,muehlbauer/otrs,moritz/otrs,s7design/otrs,brandonshults01/otrs,mburggraf/otrs,PortgasDAce/otrs,noritnk/otrs,crythias/otrs,MBRG/otrs,crythias/otrs,MBRG/otrs,rudy500/otrs,muehlbauer/otrs,oiami/otrs,mburggraf/otrs,linearregression/otrs,muehlbauer/otrs,balazj/otrs,balazj/otrs,xhoy/otrs,rudy500/otrs,balazj/otrs,mburggraf/otrs,linearregression/otrs,mbeijen/otrs-1,xhoy/otrs,balazj/otrs,crythias/otrs,StCyr/otrs,xhoy/otrs,moritz/otrs,eliasp/otrs,capeit-tto/otrs,eliasp/otrs,oiami/otrs,thorsteneckel/otrs,oiami/otrs,rudy500/otrs,MBRG/otrs,crythias/otrs,moritz/otrs,balazj/otrs,vlascoder/otrs,capeit-tto/otrs