- Adding functions for setting network source and destination masks,   and checking if a match field exists based on given type.
- Adding functions for setting network source and destination masks,
  and checking if a match field exists based on given type.

- Also adding code for checking exception returned in getDataLayerSource(),
  getDataLayerDestination(), getNetworkSource(), getNetworkDestination().

- Upating code of getNetworkTOS() to have most significant
  6-bits be the DSCP and the lower 2-bits be the ECN.

rcchan/cs168-sdn-floodlight,rcchan/cs168-sdn-floodlight,drinkwithwater/floodlightplus,drinkwithwater/floodlightplus,drinkwithwater/floodlightplus,drinkwithwater/floodlightplus,rcchan/cs168-sdn-floodlight,rcchan/cs168-sdn-floodlight,rcchan/cs168-sdn-floodlight