Implement MeterStats MP message.
Implemented MeterFeatures MP message.
Implemented PortDesc MP message.
Add TableFeatures multipart (start).

Added yqueueproperty.h
Added mptablefeatures.
More TableFeatures multipart (partial work on properties)

- Change IsPtrAligned to take two params.
- Add OFPTableFeatureProperty enum constants.
- Add InstructionID type.
- Change ProtocolRange to support 4-byte aligned properties.
- ProtocolRange::nthItem returns an iterator.
- Add Ref_cast helper to yllvm.h
Add InstructionIDRange type.