Refactor pennpipeline and update or deprecate dependent code.

Makes further progress on #16 by moving over existing
pipeline-dependent code to the new class. If we still care, we can
move it over to the PipelineClient in the future.
Fix pylint warnings.
Add PEP8 configuration.
PEP8 formatting fixes.
Fix crash on parsing empty string.
Improve ROS features for pipeline and semantics.