Cleaned up Python bindings to restore functionality:
* StaticPersistence is iterable, its nodes are usable (sign, pair, cycle)
* StaticPersistence knows how to map its nodes into Filtration indices
* moved PythonCmp into utils.h
* minor cosmetic changes
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?)