Alphashapes and Python bindings
* converted alphashapes2d to the new format
* added Python bindings for alphashapes
* added sample alphashapes.py that dynamically distinguishes between 2D and 3D
Write an audit for the data structure.
-DBOOST_UBLAS_TYPE_CHECK=0 is necessary since otherwise Boost's uBLAS gives a compile-time error
when it doesn't find sqrt for polynomials. It doesn't actually need it (e.g., for LU-decomposition,
but it looks for it during type check). (File a bug report with Boost?)