Made some changes to the balance velocity assimilation script.  Added regularization, and changed the bounds to reflect the vertical averaging error.
Added ISMIP-HOM simulation inverse_A, which demonstrates the minimization of the surface mass balance residual with respect to basal traction.
Merge branch 'master' of https://github.com/douglas-brinkerhoff/VarGlaS
Added the capability for arbitrary specification of control variables for data assimilation.  Control variables to include are now specified as a list (note that they must be valid model.* dolfin.Function type).  This is useful for including uncertainty.  For example, Greenland/data_assimilation.py now assimilates observed surface velocities with respect to both basal traction and surface velocities, assuming +/-20 percent bounds on velocities.  Many potential interesting applications of this feature.
Merge branch 'master' of https://github.com/douglas-brinkerhoff/VarGlaS