Mavenizing the project

In this pull request I 'mavenized' the whole project, so that it can be integrated into other projects by using maven's standard dependency resolution mechanism.

Due to maven's compiler infrastructure I had to remove the com.sum-internal IndentingXMLStreamWriter and replace it by the one from the stax-utils project in #65a5481.

Additionally I have altered the directory structure so that it follows the default maven conventions.

Would be kind if you merge this request.

Best regard,
Benjamin