Add matched outvar based on depvar into vector of vector of outvars
Push outvar based on human readable string for which OutVar::name = matched token. OutVar::name being not empty will be used to differentiate a depvar-based outvar from a human-readable outvar. Depvar-based outvars can directly access solution arrays using their field. Human-readable outvars need a mechanism (a function) to read and compute their variables from solution arrays. The 'getvar' function, used to compute a physics variable from the numerical solution is assigned after initial migration and thus not assigned here (during parsing).