Improve MockPropertyDefinition regarding some unsupported getter methods

How about improving MockNode, MockProperty and MockItemDefinition a bit in the following?

1. Currently org.onehippo.repository.mock.MockProperty#getDefinition() always creates a new MockPropertyDefinition (child of MockItemDefinition) instance unnecessarily. I think we can keep single member instance in MockProperty.
2. Currently MockPropertyDefinition (and MockItemDefinition) doesn't implement #isProtected(), #getRequiredType(), #isAutoCreated(), and #isMandatory(). #getRequiredType() can be supported by using MockProperty#type, and the others can simply return false by default. And it can have setter methods. Then unit test can take advantage of them.

What do you think? Doesn't it look like something someone can contribute?

ref) community thread: https://groups.google.com/forum/#!topic/hippo-community/xmkUlXNdgGc