Updated Java types according to new design
1. Removed type serializers, added (write|read)[0-9]*Byte[s]?(ChannelBuffer) method to value types instead.
2. Updated Masked fields for IPv4, IPv6 with specific string methods.
3. Added value types for other fields from the spec
4. Updated unit tests accordingly
5. Changed java_type.py to support multiple read/write operations per type, per OF version.
Merge into master from pull request #39:
Java_gen: improvements to the value types, courtesy of Yotam (https://github.com/floodlight/loxigen/pull/39)