added test application for mesh reading, fixed some bugs, reading and creating a mesh is working now; Mesh is (for now) a friend of Node, this should be fixed soon.

changed size_t to unsigned; included a few (yet unimplemented) methods for mesh-consistency checking

put nearly the whole CG method working loop into #pragma omp parallel to avoid overhead for parallelization

try to improve speedup using other OpenMP pragmas, reducing the number of parameters of function scpr and omit a initialization of a vector

- applying changes to interfaces