Improvements to internals and bugfixes

This release sees a series of internal improvements to simplify input parsing and minimize the dependency on the Boost libraries.
Notable points:

• An updated version of the pcmsolver_new API function has been introduced.
  The full name of the function is pcmsolver_new_v1112 (to avoid API breakage)
  and accepts as additional argument the name of the parsed input file
  generated by pcmsolver.py. This allows to decoupled parsing and writing out
  the parsed file, in case directory-specific operations have to be performed
  by the host program.
• Moved python scripts from bin/ to bin/pcmsolver/ and introduced bin/pcmsolver/__init__.py.
• The parse_pcm_input function returns the parsed input as a string without
  saving it to file. The old behavior can be recovered by setting the
  write_out argument to True.

Read the change log for exhaustive information. Consult also the list of issues