Part of what makes this work is the test implementation of TransportManager.
This PR is pretty straightforward. A few gotchas though:
* A message signing test was moved into `JacksonTests` because that is
where the signing actually happens.
* A CRDT serializing test was moved there as well. It's the best place
for now.
* No UDP tests at all. I plan to fix that in a bit. Reasoning is that it is
difficult to test any TransportManager implementation without bring up
a full stack. I plan to address this in the future (GOSSIP-83).
* Simple round trip Jackson serialization tests.
With these changes, it should now be possible to create alternate serialization (e.g. Gson or native) and transports (like HTTP).
To make this PR reviewable I decided against creating new modules right now. That can be done subsequently in another PR that doesn't modify any code.
* Creates two new interfaces: `TransportManager` and `ProtocolManager`
* Implementation classes must honor a common constructor interface
* Includes UDP and Jackson implementations of those.
* `AbstractTransportManager` has a lot of boilerplate that includes:
* starting the active gossiper, and
* starting the passive gossiper.
I spent some time trying to polish the implementations to become less dependent on references to `GossipManager`. I still feel there is a lot of room for improvement.
* remove redundant parameter from method call.
* remove uncessary threadpool.
* Simplify `GossipCore.sendOneWay()`
* Cleanup useage of `MessageInvoker`
* `DefaultMessageInvoker` replaced by a factory
* `MessageInvokerCombiner` replaced by same factory
* Alter `MessageInvokerTest` to not rely on specific types
* Remove type assertion from `GossipManagerBuilderTest`
* Merge `MessageInvoker` with `MessageHandler`
* This required changing method signature return type from `void` to `boolean`.
* add *.ipr to .gitignore
* modify existing pom to be a parent. create new pom for gossip-core.
* I left all properties and dependencies in the parent, as they seemed to be a fairly general set of dependencies.
move all the code.
* rename parent module: gossip -> gossip-parent
* move dependencies into child module
