Reworking cobra model/reversibility
Drawing reversibility works with new maps and models.

TODO backport to old imported maps
added example for tests to repo
Test with example.json can from from any directory
Fixes for reversibility.

- Segments remember reaction coefficients.
- Displacement of segment from metabolite now depends on presence of arrowhead.
Lots of new unit test. Fixing the reversibility code.

TODO set up multiple reaction and metabolite datasets
More consistent and less redundant handling of bigg ids
map spec file
Loading maps according to spec
add beziers when absent in an imported map
Fixes to map loading and saving for spec. Began removing unnecessary scales
Removed a bunch of unnecessary scale calls
Rotation issue solved. Fixes #43
fixes small bug with new reaction from scratch, and changes node_type to match dump.
Recomputing data scales (domain and range) when drawing new nodes
Fixed bugs with reaction drawing and data
Fixed svg export to load entire map into Illustrator.

Fixes #37
Fixed direction arrow
Case agnostic search w alphabetical results
Supporting multiple datasets & data styles parameters:

Color, Size, Diff, & Abs