Removed auto-start on subgraph, resolves #229.

If a subgraph is loaded via the component loader, the graph will not be automatically started if there is no `start` port available.
Defaults now being sent for subgraphs, resolves #230.

Changed the order of the port removal in `ComponentLoader` and updated the `Graph` component to call the network's `start` function instead of just `sendInitials`.
Subgraphs now selectively sending defaults, resolves #243

Defaults on a subgraph's input port will only be sent if that port hasn't been attached to from the parent graph.
Merge pull request #246 from hayesmg/master

Resolution to #229, #230, and #243