Added 2 new options to the filter extension: parentOnly & displayAllChildren

* parentOnly is the opposite of the existing childrenOnly option- it will traverse only nodes that are parents (have children). If both parentsOnly and childrenOnly are enabled, they will cancel eachother out and traverse all levels of the tree
* displayAllChildren will mark child nodes as sub-matches if its parent is a match (useful for searching just at parent levels, but still want to display the child noes)
Merge branch 'master' of https://github.com/pamtaro/fancytree