- Fixed HTML doc formatting in pdp.xsd and improved content.

- Upgraded authzforce-ce-core-pdp-api version to 16.1.0 adding
PolicyProvider#getCandidateRootPolicy() interface
- Changed PDP config XSD
	- Simplified versioning (version="7.1" and remove minor version from
namespace)
	- 'rootPolicyRef' no longer mandatory. If not specified,
PolicyProvider#getCandidateRootPolicy() on the 'policyProvider' is used
to specify the root policy
- Added CoreStaticPolicyProvider#getCandidateRootPolicy() to implement
PolicyProvider#getCandidateRootPolicy()

	- Changed PolicyProvider API. See CHANGELOG on core-pdp-api repository.
- Fixed #38 (GitHub)
	- Removed CoreRootPolicyProvider
	- Replaced CoreRefBasedRootPolicyProvider with CoreStaticPolicyProvider

Signed-off-by: fossabot <badges@fossa.io>

- Upgraded authzforce-ce-core-pdp-api dependency: 12.1.0 -> 13.0.0
- Implementation of feature requested in Github issue 10 (with unit
tests): creation of (XACML) AttributeValues from standard Java types

- Fixed #9 (github) and added unit tests