Change function name GMB_sendModuleRqst to GMB_callModuleService

This is to comply with GenoM vocabulary: a module has services and
ports, we call a service and we read a port. Thus, to follow the
idea of GMB_readModulePort, the function for services is
GMB_callModuleService.
Improvement for managing the GMB_native_functions/ folder.

The GMB_native_functions/ folder can already exist when calling
GMB_genomixConnect, it can happen when MATLAB is closed without
calling GMB_genomixDisconnect, and the folder can contain old
functions if GMB_loadModule was not called for some modules. In this
case, it is better to remove the old folder, and create an empty new
one, to be sure that we don't have some old invalid functions left.
Code improvement