(state < relevant state) or (residuum < relative tolerance * state)
since the relevant value for the state variables depend on their nature and can vary by large scales (e.g. volume fraction: 1e-10, dislocation density: 1e5) it is not possible to set a unique value. instead the constitutive law has to decide what is relevant. therefore, all constitutive laws now read in parameters from the material.config that determine the values for relevantState [@luc: in dislobased law relevant State is for the moment generally set to 1e-200, so no additional parameters necessary in material.config. if you also want this feature, we can still implement it, no big deal]
- added sanity checks in constitutive_nonlocal.f90
- corrected coordinate transformation for backstress calculation in constitutive_nonlocal.f90
- corrected equations for evolution of dipole dislocation densities (athermal annihilation and formation by glide)