Formatting.
Refactored scale factors into their own class.  Not replaced main project sfs yet
All old tests pass.  Need new tests for linear scale factor specifically
Work on implementing sf groups using the new custom dict in utils
Work on implementing sf groups using the new custom dict in utils
SF groups no longer crash but doesn't work very well at all
Fixed project calling LinearScaleFactor functions with wrong name
Code for plotting simulations of all variables in a given simulation
Trying SymPy common subexpression elimination to simplify complex models.
Fixed SymPy cse bugs
Added untested support for shared, global parameters.
Fixed shared global parameters
FIX: Bug in scale factor prior gradient
Import syntax cleaned up.
Cleaned variable names a bit (scale_factor -> sf)
Added option to enable jit after building an object, to make it easier to pickle projects/models.
Added option of specifying model_name
Added project_description field
Partial refactoring.  Adding option to calculate model Jacobian
BROKE LOTS OF THINGS - refactored things from model to project