Openlow 1.3#serializer

About the custom serializer problem you mentioned before in the google group, I have tried to create a custom serializer and it works now,  Since the flow format has a different between the OpenFlow versions, I only supoort the OF1.3 now.

Solution
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1. Create new type StatsReply to encapsulate the return value of  the method retrieve on SwitchStatisticsResource.java
2. Adding a custom serializer to serilize the StatsReply.

Limitation
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1. It only supports the flow type of statistic.
2. It only supports the OpenFlow 1.3

To Do
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1. Testing all fields of the OFMatch and OXM message.
2. Support other statistic type
3. Supoort other OpenFlow type (1.0, 1.1,1.2)

Output
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Here is the [output](https://gist.github.com/hwchiu/5437a9b5e038ce16c45a) from the "curl -s http://localhost:8080/wm/core/switch/00:00:00:00:00:00:00:01/flow/json" now. 
Do you have any idea about the output format? i have no idea what is the best way to present the instruction and actions.
Besides, do you know how to get the current connection version? I need to this information to make the 
serializer executes different function for each OpenFlow version.

If you have any advice make this better, please tell me, thansk