introduce libosmocore_init() to replace individual initialization calls
The typical libosmocore-using program is calling a plethora of *_init() functions, basically one for almost each sub-system within the library. Let's keep the old ones for compatibility, but have something like a global
libosmocore_init() function that could be used as a one-size-fits-all solution. Sure, we might start some timers that in the end we don't need, but having simpler/maintainable code is equally important.