Add matched outvar based on depvar into vector of outvars
Push outvar based on depvar: use first char of matched token as OutVar::var, OutVar::name = "" by default. OutVar::name being 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).