Added Eclipse 2022-06 target and migrated to Java 11

It's hard to use Gendoc in current Eclipse versions. So I added 2022-06 target.

We use Java 11 in our project and 2022-06 was the last Eclipse release before migration to Java 17. That's why I choosed that target. I think on the next merge request we can add a newer target based on Java 17.

Also I fixed some code warnings.

Updated JTidy jar-file, because old version caused the following error: "The package org.w3c.dom is accessible from more than one module: , java.xml"

The problem is that Maven-build is failed on last project org.eclipse.gendoc.services.xlsx.tests with the same error "The package org.w3c.dom is accessible from more than one module: , java.xml". I don't understand how to fix it. To reproduce the error just run:

mvn clean verify -DskipTests

The second problem is that tests in org.eclipse.gendoc.services.pptx.tests are failed with error "Workbench has not been created yet":

Running org.eclipse.gendoc.services.pptx.tests.PptxSimpleTest
Tests run: 1, Failures: 0, Errors: 1, Skipped: 0, Time elapsed: 7.108 s <<< FAILURE! - in org.eclipse.gendoc.services.pptx.tests.PptxSimpleTest
simpleTest(org.eclipse.gendoc.services.pptx.tests.PptxSimpleTest)  Time elapsed: 7.067 s  <<< ERROR!
java.lang.NoClassDefFoundError: org/eclipse/papyrus/infra/ui/emf/databinding/EMFObservableList
        at org.eclipse.gendoc.services.pptx.tests.PptxSimpleTest.simpleTest(PptxSimpleTest.java:20)
Caused by: java.lang.ClassNotFoundException: An error occurred while automatically activating bundle org.eclipse.papyrus.infra.ui.emf (452).
        at org.eclipse.gendoc.services.pptx.tests.PptxSimpleTest.simpleTest(PptxSimpleTest.java:20)
Caused by: org.osgi.framework.BundleException: Exception in org.eclipse.papyrus.infra.ui.internal.emf.Activator.start() of bundle org.eclipse.papyrus.infra.ui.emf.
        at org.eclipse.gendoc.services.pptx.tests.PptxSimpleTest.simpleTest(PptxSimpleTest.java:20)
Caused by: java.lang.ExceptionInInitializerError
        at org.eclipse.gendoc.services.pptx.tests.PptxSimpleTest.simpleTest(PptxSimpleTest.java:20)
Caused by: java.lang.IllegalStateException: Workbench has not been created yet.
        at org.eclipse.gendoc.services.pptx.tests.PptxSimpleTest.simpleTest(PptxSimpleTest.java:20)

To reproduce it build as follows:

mvn clean verify

Maybe it's not supposed to be build that way?

Could you please help to fix it?