WIP: Python 2.7 DriverProxy native extension

[Lukas-Dresel]

A preliminary implementation of a Python wrapper for ABC. Currently in a WIP state, some ref-counting is still missing. This will be updated as we go. Do NOT merge this PR yet please!

This currently has a bunch of quirks, like requiring the output/ directory to exist that I haven't worked around yet.

[Lukas-Dresel]

Current usage example:

In [1]: import PythonABCSolver

In [2]: p = PythonABCSolver.DriverProxy(0)

In [3]: csts = """(set-logic QF_S)
   ...: (declare-fun var_abc () String)
   ...: (assert (= var_abc "abc"))
   ...: (check-sat)
   ...: """

In [4]: p.isSatisfiable(csts)
I0129 15:47:05.819499 24154 SyntacticOptimizer.cpp:99] and has 1 children
I0129 15:47:05.820063 24154 SyntacticOptimizer.cpp:99] and has 1 children
I0129 15:47:05.820276 24154 SyntacticOptimizer.cpp:99] and has 1 children
Out[4]: True

In [5]: p.getSatisfyingExamples()
Out[5]: {'var_abc': 'abc'}