RF: expose set_openssl(), set_destroy()

idea is to permit setting when used via import:
import pyfilesec as pfs
pfs.set_openssl(path_to_openssl)

and interactively will report current:
>>> import pyfilesec as pfs
>>> pfs.set_openssl()
('/usr/bin/openssl', 'OpenSSL 1.0.0-fips 29 Mar 2010', True)
DOC: demos, readme, easier command-line (using an alias)