Add new extremely fast direct monte-carlo method

[ahnitz]

This is the work in progress PR for a new extremely fast sampling algorithm. It requires some externally generated files (not provided yet). The code is in preview / toy stage at the moment.

Todo:

• simplify the pregenerated storage format and provide script + exapmle that makes the pregenerated input.
• add options to the few tunable knobs
• add multi-process / mpi support in
• sanity checking of input
• [longer term]
  • allow more flexible change of prior