add_* shortcut

[thunder-hammer]

This should be discussed before we implement it. wait to work on this for discussion results to be posted.

The add_* api calls that exist in all of the different classes could be replaced with a simple add call that at least first class components have. behind the scenes these calls could simply sort by the type of the passed in data and then call the corresponding function.

This may be a version 2.0 feature or not a feature depending on perceived merit. definition.add_child and reference should not present an issue but the clarity may be reduced (definition.add(instance)) may be unclear.