Removing ElTopo

Since ElTopo does not need any abstractions of this library, I decided to move the related code to it's own repository. That also makes SurfaceGeometry now cross platform.

First alpha release

The library is now functional and available for julia 1.0. The binary dependencies of ElTopo are now delegated to ElTopoBuilder and ElTopo.jl. The support for generating meshes with CGAL and Distmesh is killed. See Meshing.jl for making an alternative.