fixed compile error
added multi-connect option with 5 different modes:

1. shift-click manual multi-connect
2. two selected objects multiple outlets to multiple inlets
3. two or more selected objects connecting to one unselected one
4. one unselected connecting to multiple selected ones
5. multiple selected ones connecting to one's multiple inlets OR the other way around (determined on whichever mode gives more valid connections)

Option 1 requires use of shift. Other options are based on what is selected at the time of making the first connection (others are automatically created based on conditions). Later consider adding special undo that undos all connections in one step, rather than multiple steps.