Supporting the SBML layout extension

Motivation: Researchers studying large or complex biochemical networks would benefit from the ability to automatically create lucid visualizations and store them in a portable and widely accepted format. Summary: Two modules, SBMLSupportLayout and SBWAutoLayout, support reading, creating, manipulating and writing layout information for biochemical models. SBMLSupportLayout can read, update, add and render model layout information. SBWAutoLayout can automatically layout models, graphically manipulate model layout and generate layout information for models without layout information.