Embrace more types on ObjectBuilder? Enable JSON-Schema linkage

JsonObjectBuilder is a very convenient API and has the advantage in current form to not loose immediately the format of the underlying data (BigDecimal/BigInteger, long, ....). However I think it should cover what developpers consider as "primitives". To be accurate I think we can use json schema specification as a basis.

What is missing IMO is:

- date-time (can use java 8 types and formatters as "normalizer" when it goes to JsonObject)
- date (can use java 8 types and formatters as "normalizer" when it goes to JsonObject)
- time (can use java 8 types and formatters as "normalizer" when it goes to JsonObject)
- email, hostname (think these ones can be collapsed with string since no other format uses this information I think)
- ipaddress (java.net)
- resource identifier (URI)
- regex (this one is to refine since I'm not sure a Pattern can easily and accurately be converted to a string all the times)
- ...

The most important (and urgent) item is likely about the dates but longer term it would be very good to have an API allowing users or implementations to generate a schema from the builder API transparently (just decorating the default implementations).

Begin by reviewing the JsonObjectBuilder API and the JSON Schema formats described in the issue, prioritizing date-time, date, and time with Java 8 types and formatters. Done requires a narrowed, agreed scope for supported types and conversion or schema behavior, with corresponding tests identified before implementation.

Written by the indexing model from the issue text.