Refactor netty handlers.

[hechaoli]

1. Rename OvsdbClientHanlder to OvsdbConnectionHandler. It is now only responsible for notify connections. Also merge HeartbeatHandler to this handler.
2. Add JsonRpcHandler that handles the inbound JSON-RPC messages.
3. Add OvsdbClientImpl that can be constructed from a Netty channel.

Signed-off-by: Hechao Li hechaol@outlook.com

[coveralls]

Pull Request Test Coverage Report for Build 63

• 156 of 164 (95.12%) changed or added relevant lines in 4 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.003%) to 98.89%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
ovsdb-client/src/main/java/com/vmware/ovsdb/netty/JsonRpcHandler.java	26	30	86.67%
ovsdb-client/src/main/java/com/vmware/ovsdb/service/impl/OvsdbClientImpl.java	73	77	94.81%
<!--	Total:	156	164	95.12%	-->

Totals
Change from base Build 59:	0.003%
Covered Lines:	1693
Relevant Lines:	1712

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💛 - Coveralls