Convert heading ids

At the moment, XWiki's DokuWiki parser assumes that DokuWiki doesn't use heading ids. However, that's wrong, DokuWiki automatically generates heading ids like XWiki, just with a different algorithm. Heading ids can be used in links to specific sections or in the include plugin to include a specific section. The extension should re-implement DokuWiki's id generation algorithm. There are then two solutions:

1. Add the generated heading ids as explicit ids in the syntax
2. Use XWiki's id generate in parallel to compute a mapping between DokuWiki and XWiki heading ids and then adjust all links (and include macros when they should be supported)