ISBN & URL support, better edges.

This demo release added support for the following:

• Detecting ISBN number of books, and automatically find online resources upon double click.
• Detecting and opening web URLs.
• Edges are now curved. They now automatically adapt to node width, position, and snapping.

Things fixed:

• Replaced the handle area design with dots.
• Fixed an issue where a blue note does not show highlighted borders when being dropped with another node.

Known bugs:

• Multiple notes can be snapped under the same note, causing them to overlap.