flow_table: Remove counters dictionary
flow_table: Remove counters dictionary

Various things (including but not limited to counters) were stored
in a dictionary.  They're now just kept in attributes.

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