Remove Carve boolean

We've got quite comprehensive BMesh based implementation, which is way easier
for maintenance than abandoned Carve library.

After all the time BMesh implementation was working on the same level of
limitations about manifold meshes and touching edges than Carve. Is better
to focus on maintaining one boolean implementation now.

Reviewers: campbellbarton

Reviewed By: campbellbarton

Differential Revision: https://developer.blender.org/D3050