* render generic output (sigma.js json) for ingestion -> unity
* move from inheritance -> better encaps
* sort out fore vs back color
* move out any graphviz specifics from main models, e.g. colorize
* clean up init options + render attributes - not v clear / overlapping
* separate style from domain-specific elements (can use same view-manipulation selection mechanisms)
* make style attributes well defined -> less leaky + explicit graphviz passthroughs