libopenflow: Better defaults for action headers
libopenflow: Better defaults for action headers

(Akbar fixed this for the enqueue action in the previous commit; this fixes it
for the rest of them, I think.)

Some actions were just initializing their type field to 0.
In the case of actions where there is only one valid option (e.g., SET_NW_TOS),
these are now set to the single option.
Other types now default to None, which will at least cause an exception if
you forget to set it.  Additionally, these can now be set in the constructor.
Lastly, for the ones that have a src/dst pair (e.g., OFPAT_SET_TP_SRC/DST),
there are now helper class methods, like ofp_action_tp_port.set_src(<port>).

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