l2_multi: Various improvements/changes
l2_multi: Various improvements/changes

This does some cleanup and reworking of l2_multi:
* Install paths in both directions
* Set in_port in flow entries
* Wait for path to be installed before forwarding packet
* Various cleanup/modernizing

Note: you must now run discovery explicitly.

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