Content EXIM relying on non-v16 forge plugin versions

Content EXIM relies on 2 other forge plugins (POJO bind and Gallery Magick)

Most importantly

In the released 6.0.0 version, the versions for the depending plugins weren't updated to their v16 equivalent
<forge.hippo-pojo-bind-jcr.version>2.0.0</forge.hippo-pojo-bind-jcr.version> - should be 3.0.1
<forge.gallery-magick.version>3.0.2</forge.gallery-magick.version> - should be 4.0.0

Other improvements

docs can be removed and recreated on master because the latest skin is not applied to all the pages and the logo is still the old one

all the below versions are defined in the parent pom so can be removed and adjusted in the plugin
<lib.junit.version>4.13.1</lib.junit.version>
<lib.easymock.version>3.4</lib.easymock.version>
<lib.slf4j.version>1.7.30</lib.slf4j.version>
<lib.log4j2.version>2.17.1</lib.log4j2.version>

this can be adjusted
<issueManagement>
<url>https://issues.onehippo.com/projects/HIPFORGE</url> -to /FORGE
</issueManagement>

this can be removed
<extension.wagon-svn.version>1.9</extension.wagon-svn.version>
and
<extensions>
<extension>
<groupId>org.jvnet.wagon-svn</groupId>
<artifactId>wagon-svn</artifactId>
<version>${extension.wagon-svn.version}</version>
</extension>
</extensions>