Refactoring: 'refactoring-python-preprocessor':

tarantool preprocessor routine was changed:
 - Now 'exec obj ...' command will translate to obj.execute(...);
 - New command 'send' and 'recv' was added. 'send obj ...' and 'recv obj
   ...' will translate to 'obj.send(...)' and 'obj.recv(...)'
   respectively;
 - New command modifiers 'silent' and 'verbose' was added. Verbose
   (silent = False) value is default.

Tests - box, box_big, box_memcached, box_replication was updated.