Improved assembly

Yesterday I learned how to do variable argument macro's in Julia and based on my new knowledge implemented the bilinear assembly (and linear assembly) with material parameters using them. Thus, now there is only a single macro for bilinear assembly and bilinear assembly with a material parameter (or some other node-wise defined parameter). Next goals for the Julia-code:

• Assembly of the boundary terms
• Faster mesh refinement
• Simple geometry representations for 2D-domains
• 3D-linear tetrahedral element
• ...
• and in a distant future
• ...
• Geometry tools
• Additional elements: p-refinement, vectorial elements (i.e. Raviart-Thomas)
• Isoparametric mappings
• Simple geometry representations for 3D-domains

Some of these might be too much to realize in practice but there is always hope.