INT-3104:Add auto-start attribute to Gemfire Adapters

Add auto-start attribute to Gemfire Adapters
Gary is right: this attribute is covered by superclass and in most cases it is for the `endpoint`, not its `messageHandler` or `messageSource`.
And it is a rule: if we provide `auto-startup`, we should allow to configure the `phase`, too.
No need for you here: just for the future.

So, you PR should be shorter: just XSD and tests.