Authoring tool coming along

The generic H5P authoring tool is now able to edit much of the boardgame content. It is also able to create new nodes based on the libraries in Boardgame. It can create Multichoice nodes, Questionset nodes and new Boardgame nodes, but we have some bugs to sort out before the new nodes created using the H5P Editor works perfectly.

We've also added library support for the H5P editor. This means that an H5P package may contain an H5P Editor library that expands the capabilities of the Editor.