Added OFBufferId class to represent OF buffer ids
Return enum types for fields in OFPortDesc and OFFeaturesReply
Return OFPNiciraControllerRole enum in OFNiciraControllerRoleXXX messages
Incorporate review feedback for OFBufferId code
Combine per-error-type error code enums into a single error code enum

- also suppress code generation of OFPortNo which is already handled
  by the pre-written OFPort class
Merge branch 'master' of github.com:floodlight/loxigen

Conflicts:
	java_gen/java_model.py
	java_gen/java_type.py
Added wire type to ofp_nicira_controller_role enum
Merge into master from pull request #72:
Support for OFBufferId and enum field types for OFPortDesc and OFFeaturesReply (https://github.com/floodlight/loxigen/pull/72)