Cleanup + unify tab/joint handling

Tabs and joints are just different ways of attaching EdgePorts, so should probably be handled accordingly.

• Remove Drawing classes/methods in favor of standard regular Face and HyperEdge types
• Auto-tabify #22
• Cleanup implementation
• Figure out how to represent general design-specified connections vs unique user-specified joining options

changed milestone to %0.4.x

added bugusability cleanup labels

marked this issue as related to #22