Tahoe Code SVN development

Potentials now depend r^2 instead of r

always keep the associated solid element group synchronized when running through
element calculations with Top-Next

need to reset the format of the element stiffness matrix based on changes to
the concentration type

changes to support concentrations with respect to the current configuration. The tangent
modulus still needs to be implemented, so use the finite difference approximation for now.

Updating Band tracing algorithm. Still not working. Rewriting dieterich friction
model in terms of arcsinh form, and using generalized trapezoidal
scheme. Also not working yet.

corrections to code for concentrations in current configuration

write current and reference concentrations to output

implemented changes to support concentrations expressed either with
respect to the current or reference configuration

adding constructor with additional parameters: dof and nip of lambda field

removed #ifdef __DEVELOPMENT__