Gmsh path is not written properly into path file at windows installation

[hpreiss]

Gmsh seems to live in gmsh/gmsh.exe instead gmsh/bin/gmsh.exe .

[alexblaessle]

Since commit 1de8324 PyFRAP has a path management tool.

However, we still need to adjust the paths automatically at installation.

[alexblaessle]

@hpreiss, commit 7792ecc should fix the addition to PATH. Can you confirm?