Extend the Inexor Tree with links to other nodes

[aschaeffer]

Goal

A node within the Inexor Tree links to another node in the tree. This feature can be used to link sub trees into instance trees.

Implementation details

• [x] New datatype link
• [x] Node.value references to the targetNode
• [x] getChild(name`)
  • returns the targetNode object
• [x] addLink(name, targetNode)
  • specialized version of addChild(name, datatype = link, value = targetNode)

[aschaeffer]

Done: https://github.com/inexorgame/inexor-flex/commit/e5f8cfb558b16db69133fa3838380d5c448353bc