pymapistore: add message_get_properties and message_set_properties

Nah, this is a *very* dirty hack (or not, we'll see) and I need your help to resolve the puzzle.

The thing is that Samba has already loaded libpythonXX.so.
So this function works quite nicely.
The pythong script loaded by this function doesn't work though when it loads a library that
depend on Python API calls.
This never happens for instance if I test with mapistore_test program (that directly loads mapistore.so etc).
This happens, of course, only when running in Samba context. So it took some time to realize, that
python libraries got loaded with !GLOBAL flag set. Hence not accessible down the chain in child processes.
So, here it goes the hack - pre-load again with GLOBAL flags set.

IMO, it is quite ugly. And I will appreciate any ideas how to make it better looking