finite area integration

This merge includes the finite-area port from Hrvoje Jasak, a number of integration fixes and preliminary post-processing of finite area meshes/fields.

References

Tukovic, Z: The Finite Volume Method on Domains of Changeable Shape, PhD Thesis, University of Zagreb, Croatia, 2005

Tuković, Željko; Jasak, Hrvoje. A moving mesh finite volume interface tracking method for surface tension dominated interfacial fluid flow. Computers & fluids. 55 (2012) ; 70-84