packet: packets have payload property
packet: packets have payload property

This is a more elegant solution to the .next field and the .set_payload()
method.  This was actually implemented a few commits ago, but was omitted
in the log (oops).  This commit actually just fixes a typo in the docstring.

PrincetonUniversity/pox,waltznetworks/pox,kulawczukmarcin/mypox,PrincetonUniversity/pox,VamsikrishnaNallabothu/pox,carlye566/IoT-POX,denovogroup/pox,kavitshah8/SDNDeveloper,MurphyMc/pox,VamsikrishnaNallabothu/pox,kulawczukmarcin/mypox,jacobq/csci5221-viro-project,MurphyMc/pox,chenyuntc/pox,andiwundsam/_of_normalize,adusia/pox,noxrepo/pox,andiwundsam/_of_normalize,xAKLx/pox,kulawczukmarcin/mypox,chenyuntc/pox,pthien92/sdn,kpengboy/pox-exercise,waltznetworks/pox,waltznetworks/pox,jacobq/csci5221-viro-project,waltznetworks/pox,VamsikrishnaNallabothu/pox,xAKLx/pox,jacobq/csci5221-viro-project,andiwundsam/_of_normalize,xAKLx/pox,adusia/pox,diogommartins/pox,MurphyMc/pox,diogommartins/pox,diogommartins/pox,noxrepo/pox,pthien92/sdn,kpengboy/pox-exercise,MurphyMc/pox,chenyuntc/pox,carlye566/IoT-POX,carlye566/IoT-POX,pthien92/sdn,kavitshah8/SDNDeveloper,jacobq/csci5221-viro-project,kpengboy/pox-exercise,pthien92/sdn,chenyuntc/pox,VamsikrishnaNallabothu/pox,kavitshah8/SDNDeveloper,PrincetonUniversity/pox,PrincetonUniversity/pox,carlye566/IoT-POX,adusia/pox,MurphyMc/pox,PrincetonUniversity/pox,kpengboy/pox-exercise,denovogroup/pox,kpengboy/pox-exercise,xAKLx/pox,denovogroup/pox,diogommartins/pox,diogommartins/pox,xAKLx/pox,kavitshah8/SDNDeveloper,waltznetworks/pox,denovogroup/pox,adusia/pox,adusia/pox,kulawczukmarcin/mypox,VamsikrishnaNallabothu/pox,carlye566/IoT-POX,andiwundsam/_of_normalize,pthien92/sdn,noxrepo/pox,noxrepo/pox,kulawczukmarcin/mypox,jacobq/csci5221-viro-project,denovogroup/pox,chenyuntc/pox