- Better cleanup after reconnecting edges in manipulation mode

- Worked around hammer.js bug with multiple release listeners.
- Improved cleaning up after manipulation toolbar.
- Added getPositions() method to get the position of all nodes.
- Added getCenterCoordinates() method to get the x and y position in canvas space of the center of the view.

- Added animation to zoomExtent navigation button.
- Improved cleaning of Hammer.js bindings.

- Added new event that fires when the animation is finished.
- Added new example showing the new features of animation.

- Fixed an initial rendering before the graph has been stabilized (introduced at fixing #131).

- Revamped the options system. You can globally set options (network.setOptions) to update
settings of nodes and edges that have not been specifically defined by the individual nodes and edges.
- Disabled inheritColor when color information is set on an edge.
- Tweaked examples.
- Removed the global length property for edges. The edgelength is part of the physics system. Therefore, you have to change
the springLength of the physics system to change the edge length. Individual edge lengths can still be defined.
- Removed global edge length definition form examples.