- Upgraded Maven parent project to 8.0.0
- As part of Java 11 migration, upgraded JAXB (Jakarta XML Bining) to v2.3.3
- Upgraded authzforce-ce-core-pdp-api to v18.0.0
- Fixed CVE on jackson-databind -> v2.9.10.8
- Upgraded authzforce-ce-xacml-json-model: 3.0.0
- Replaced findbugs maven plugin with spotbugs
- updated license headers for year 2021

- 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>