Maintain virtual MuranoPL stack trace

MuranoPL need to maintain its own stack trace that is independent on underlying Python stack trace and the fact that MuranoPL methods are executed in different green threads. Stack trace is a list of stack frames. Each stack frame has a execution pointer that allows to identify current instruction (or instruction caller). Ideally in debug mode it should be possible to access local stack frame variables as well. It should be possible to obtain current stack trace at any moment or place, pretty-print it or get caller class/object