Added parameter addLevelClass to jstree(); if true, add a class attribute "level_n" to each node, where n is the tree level (depth) of each node, starting with top level = 0.  Useful with conditionalPanel, css and jQuery.
jstree.obj: Added options to decorate nodes with leveltype attribute and/or index (path) attribute.
Changed class prefix to treedepth; removed (for now) addLevelType.
Renaming: using "depth" throughout for the distance to the root.
Merge pull request #6 from professorbeautiful/node-levels-and-classes

Node levels and classes