Document `setTitle`

update #97
Refactored drag'n'drop extension.

`dnd.onDrop(node)` --> `dnd.dragDrop(node, data)`
closed #100
Merge branch 'gridnav'

Refactored keyboard handling. Keydown handlers are now bound to the
container instead of document (Co-work with Koloto).
See ‚Tweaks - Keyboard nav.‘ for an example.
Allow to return 'preventNav' in keydown event to prevent withput
blocking keys in embedded input controls.
New method `node.navigate()` to support custom keyboard handlers
Fixed BACKSPACE on top-level nodes
`grunt dev` combines `grunt server` + `grunt watch` (trigger jshint and
less on save)