implement ability to add I/O to a Component in Group configure method

[swryan]

Some models that require self-interrogation need to be able to add I/O in components from the configure method of their containing groups. (related to POEM_003).

• implement _post_configure function
• update IndepVarComp and library components to create inputs and outputs in _post_configure instead of setup so their "add I/O" functions can be used in configure
• make list_inputs and list_outputs (self-interrogation) work on components before model is run
• add example to docs that demonstrates adding I/O in configure
• add note to docs about the use of list_inputs and list_outputs on components before the model is run