Causal cluster support

[albertodelazzari]

Starting from the UUID module issue 34 we have found no support for causal cluster writing permissions. We created a class for operational mode and instance role resolution. There are three new Maven profiles:

• a default one "default" for the execution of the current tests
• a "ha-test" profile for the execution of tests with High Availability instances (by default one master and two slaves)
• a "cc-test" profile for the execution of tests with Causal Cluster instances (by default three cores and two read replicas)

There are two base classes to extend if you want to do some tests in HA or CC:

• com.graphaware.test.integration.cluster.HighAvailabilityClusterDatabasesIntegrationTest should be extended by each test class in order to provide an HA environment. The test class must also be named with a proper suffix "TestHighAvailability", for example MyClassTestHighAvailability.
• com.graphaware.test.integration.cluster.CausalClusterDatabasesintegrationTest should be extended by each test class in order to provide a CC environment. The test class must also be named with a proper suffix "TestCausalCluster", for example MyClassTestCausalCluster.

There is also an update to the RotatingTaskScheduler class in order to provide HA and CC support (we also updated com.graphaware.runtime.config.TimerDrivenModuleConfiguration.InstanceRolePolicy)

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[albertodelazzari]

About the maven profiles we added, we have to consider to change the Travis build definition in order to handle all the profiles properly