tasks 1-3. added a 'per element' constructor to the class Matrix3x3T in utilities.h, mümmer denn au mit abgeh.
computing ths (task 4). strangely performance decreases when using functions 'getAreaInMesh', 'eval_N', 'calculateCoeffiecientsInMesh'...
changed back to the more reasonable solution (static methods were a desperate try to fix the performance thing, which still isnt fixed)
added error-code (task 5, thanks Hartmut). Memberfunctions for calculating coefficients of N_ij, N_ij itself and the area of the element given the mesh it's living in still mush slower than just copying code. Anyone can tell why?