Add Java 8 requirement for building using Maven

java.xml.bind is no longer part of Java SE (starting with version 11, was disable by default in version 10).
This change make the build fail if using Java 11.
I added a note in the "Building the project" section to warn the user.
Long term solution would be to update the project dependency to add the missing library.

Conflicts:
	pdp-cli/pom.xml
	pdp-engine/pom.xml
	pdp-io-xacml-json/pom.xml
	pdp-testutils/pom.xml
	pom.xml

Conflicts:
	CHANGELOG.md

- Upgraded dependencies:
  - authzforce-ce-xacml-json-model: 2.3.0
  - authzforce-ce-core-pdp-api: 16.3.0
  - jongo: 1.4.1

Balana and AT&T XACML.

Merge pull request #45 from authzforce/dependabot/maven/pdp-testutils/com.fasterxml.jackson.core-jackson-databind-2.9.10.3

Bump jackson-databind from 2.9.10.1 to 2.9.10.3 in /pdp-testutils

Bumps [jackson-databind](https://github.com/FasterXML/jackson) from 2.9.10.1 to 2.9.10.3.
- [Release notes](https://github.com/FasterXML/jackson/releases)
- [Commits](https://github.com/FasterXML/jackson/commits)
Signed-off-by: dependabot[bot] <support@github.com>

# Conflicts:
#	pdp-cli/pom.xml
#	pdp-engine/pom.xml
#	pdp-io-xacml-json/pom.xml
#	pdp-testutils/pom.xml
#	pom.xml

# Conflicts:
#	CHANGELOG.md
#	pdp-cli/pom.xml
#	pdp-engine/pom.xml
#	pdp-engine/src/main/resources/pdp.xsd
#	pdp-io-xacml-json/pom.xml
#	pdp-testutils/pom.xml
#	pom.xml

- Upgraded dependency authzforce-ce-core-pdp-api to 16.2.0

Conflicts:
	CHANGELOG.md
	pdp-cli/pom.xml
	pdp-engine/pom.xml
	pdp-io-xacml-json/pom.xml
	pdp-testutils/pom.xml
	pom.xml