remove boost dependency when building using setup.py

The boost library is used for an MRU cache of open decompressed files, which is needed by programs-that-shall-not-be-named which expect to be able to freely open-close-open-close compressed HSD and HCAST data.

Disabling the cache when building a strictly-python (no fortran) module will make building and distributing the library much simpler.

This should be done as a compiler flag in setup.py most likely, which should disable MRU in opensesame and opensesame2.