datapaths: Make SoftwareSwitch launchable
datapaths: Make SoftwareSwitch launchable

This probably isn't directly useful since it doesn't do much, but the
infrastructure is there to launch subclasses.

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