Support feature flags in java client

[demirkayaender]

What changed?
Similar to cadence-workflow/cadence-go-client#1103 change in go client, this PR introduces feature flags to java client so customers using java can enable/disable some features.

Why?
Without this change, customers won't be able to turn on some features.

How did you test it?

USE_DOCKER_SERVICE=true ./gradlew test --tests *testSignalingCompletedWorkflow* // with real server

./gradlew test --tests *testSignalingCompletedWorkflow*

Also tested with java samples

Potential risks

[demirkayaender]

Failure is from the integration test using older server Docker images which doesn't support the new error. On Monday, I will ask how to update the server version.

[coveralls]

Pull Request Test Coverage Report for Build 862

• 9 of 42 (21.43%) changed or added relevant lines in 5 files are covered.
• 1 unchanged line in 1 file lost coverage.
• Overall coverage decreased (-0.1%) to 71.175%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/main/java/com/uber/cadence/serviceclient/ClientOptions.java	4	5	80.0%
src/main/java/com/uber/cadence/internal/testservice/TestWorkflowService.java	0	2	0.0%
src/main/java/com/uber/cadence/internal/sync/TestActivityEnvironmentInternal.java	0	3	0.0%
src/main/java/com/uber/cadence/internal/sync/TestWorkflowEnvironmentInternal.java	0	3	0.0%
src/main/java/com/uber/cadence/serviceclient/WorkflowServiceTChannel.java	5	29	17.24%

Files with Coverage Reduction	New Missed Lines	%
src/main/java/com/uber/cadence/serviceclient/ClientOptions.java	1	55.13%

Totals
Change from base Build 858:	-0.1%
Covered Lines:	10699
Relevant Lines:	15032

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💛 - Coveralls