Reduce dependencies on YUI 2
- Added native CSS classes for Tree renderer
(named "xowiki-tree" to avoid name clashes).
- Made TreeRenderer more configurable, by providing css class names etc.
- toc includelet: replaced default (when no style is provided)
from yuitree to list + xowiki-tree.
The old behavior can be achieved by {{toc -style yuitree}}
Note that not all features of the YUI tree might be available
- The CSS variant with xowiki-tree can also be used for the folder-tree,
but so far, the bootstrap3 renderer is more nice.
