allow multiple tree layouts
allow multiple tree layouts

- Instead of getting information about trees
  by direct index manipulation, encapsulate
  such info to an OO layer
- Provide two implementations for this.
  "StandardLayout" and "InlineLayout"
- Keep it internal and local, ie. instead
  of exchanging layout objects, the tree hierarcy
  is still kept internally (instead of recursive
  linked layout objects) and functions still
  work with a tree based interface
- broaden scope for input/output formats

csabahenk/HTMLi