S4 class for a list of out-fluxes indexed by source pool name
OutFluxList_by_PoolName
as.numeric,OutFluxList_by_PoolName-method
by_PoolIndex,OutFluxList_by_PoolName,character,character-method
UnBoundNonLinDecompOp_by_PoolNames,InternalFluxList_by_PoolName,OutFluxList_by_PoolName,character-method