Tahoe Code SVN tahoe

changes to allow run without ANY active degrees of freedom, i.e., Tahoe
as a material point simulator.

construct nodal velocity for materials that need it for quasistatic simulations

(1) changed NeedVel - model does not need nodal velocities
(2) changed flag so that polar decomposition does not perturb repeated roots

allow for empty systems

fixed LinearSolve for zero length system

fixed error in header list

output coefficients of cubic spline hardening function

updated documentation of material 9 for new yield function and new 3D implementation

added support for arbitrary isotropic hardening functions

- removed redundant calls
- corrected update to trial elastic state