Updated parameter introspection and traj parameters

Summary

Trajectory parameters now pull introspection data from constituent phases even under MPI. Phase parameters now allow for a mixture of static and dynamic targets.

Deprecated `static_target` in favor of `static_targets` which is a set of those targets which are static.**

Previously option static_target was an all-or-nothing setting for a parameter. Now option static_targets is a set of targets to which the connection is treated as a static one (not sized with the number of nodes in the phase. Dymos will use introspection to attempt to determine which targets are static. static_targets may still be provided as an "all-or-nothing" True or False option.

Changes to internal method `_get_targets_metadata`

The method now returns a dictionary keyed by target path and associated with metadata (shape, units, value, tags) of the given target.

Added new introspection method `_get_common_metadata`

This method will accept targets and a metadata key, and then return the value of the given metadata key if it is shared across all targets. This is useful when trying to infer the units or shape of a parameter.

Changes to `ODEEvaluationGroup`

Under the ExplicitShooting transcription, ODEEvaluationGroup is required to perform its own introspection since its configure method occurs before that of the parent phase. This group is now passed copies of the time, state, control, and parameter options dictionaries of the parent phase, so that results of its introspection will not conflict with those of the parent phase.

Related Issues

Resolves #963

Backwards incompatibilities

None

New Dependencies

None

OpenMDAO / dymos