pmp-library/pmp-library: 3.0.0

We are pleased to announce version 3.0 of the Polygon Mesh Processing Library! This is a major release with several additions and API changes. Highlights include:

• We integrated a polygon Laplacian that enables several algorithms to work on general polygon meshes, including smoothing, parameterization, fairing, and curvature computation.
• The geodesics in heat method has been added.
• The algorithms API has been revamped to use a simple function-based interface.
• New interactive online demos integrated into the algorithms guide.
• We no longer use git submodules for handling third-party dependencies.
• Upgrade C++ standard to C++17
• ... a whole lot of smaller fixes, cleanups, and improvements

See the changelog for a full summary of changes.