Migrate JavaEE to Jakarta EE

Based on #186

Remove news from project README.md.

It should be on project's website.

Align with new XPP dependency.

Version 2.1.2 has been skipped.

Branch 2.1.x is built for Java 1.8.

Use JDK 1.8 for build this.branch.

version 2.1.1

Change minimum Java version to 8 for branch 2.1.x

Fix CI with OpenJDK 7 - use HTTP instead of HTTPS for Gradle (#31)

Fix CI with OpenJDK 7 - use HTTP instead of HTTPS for Gradle