Fixed getting location for placing the particles on the narrow band s.t. also valid for negative domain origin.

Adapted getting Surface Normal from Level Set Function s.t. normal has length = orthog. distance to surface.

Changed distance in placing of mirror particles. Now, normal vector should have length = distance to the surface.

Merge branch 'new_sussman_enoweno' of ssh://git.mpi-cbg.de/openfpm/openfpm_numerics into new_sussman_enoweno

Changed structure of templated functions in Eno/Weno s.t. it can be used with less params. Adapted UpwindGradient accordingly.