Add another loop to assembly procedure

Yet another loop, but this way we can preallocate matrices when
constructiong local matrices of elements with same dimensions (which is
the case in practice)

src/assembly.jl

@@ -73,3 +73,11 @@ function assemble!(problem::Problem, time::Real, ::Type{Val{:mass_matrix}}; dens
     end
 end
 
+function assemble!(assembly::Assembly, problem::Problem, elements::Vector{Element}, time::Real)
+    warn("assemble!() this is default assemble operation, decreased performance can be expected without preallocation of memory!")
+    for element in elements
+        assemble!(assembly, problem, element, time)
+    end
+    return nothing
+end
+