JCR-4085 - always include property type data for DOUBLE

[justinedelson]

As discussed in https://issues.apache.org/jira/browse/JCR-4085, JSON only has a single numeric type, so type inference cannot be used to differentiate between whole numbers in a LONG and DOUBLE field. To compensate for this and allow clients to properly understand the property types, DOUBLE properties should always contain type information, as is already done for DECIMAL types.

[reschke]

Any chance to add a few unit tests?

[justinedelson]

added unit test for this behavior. My preference would have been to add a dependency to something like https://github.com/skyscreamer/JSONassert, but it seemed like overkill to add an additional test dependency just for this one case.