Mesh connectivity information not defined for all scenarios in 2D and 3D cases

[IshaanDesai]

Currently mesh connectivity information is only defined for 2D cases in the form of triangles (constructed from edges). For 2D cases one could also define quads. Additionally for 3D cases, connectivity information in the form of tetrahedrons and cuboids can also be defined. The current implementation needs to be extended to cover more types of connectivity information that preCICE can understand.