Create a schemagen task to replace the schemagen command line tool.

[swpalmer]

Create a schemagen task to replace the schemagen command line tool that is removed in Java 11.

JAXB is very hard to use with Java 11 because not only are the modules not there, but the tools are not even produced anymore. Documentation on how to run schemagen with Java 11 is very disappointing. The tools are apparently available as maven artifacts, but not the launch scripts. A JAXB plugin that offers tasks for all the JAXB functionality removed in Java 11 would be a tremendous help.

[wdschei]

Thanks for the suggestion on this. We are getting ready to migrate our main project out of the Java 8 land and will be updating this plugin to play happily as well. We haven't investigated this at all from this plugin's perspective yet, so we will definitely be trying to figure out the best way forward. Any suggestions are more than welcome.