Make OFStatsRequest parameterized with the StatsReply
OFPort: remove wrong NONE=0 constant
Introduce TableId value type
java_gen: make OFFactory be a XidGenerator
java_gen: made OFValueTypes Comparable
Merge into master from pull request #75:
Various improvements for vft-demo (https://github.com/floodlight/loxigen/pull/75)