major refactoring and some features. Changes are:
- Agent.send_command now blocks calling thread until reply and returns reply in this thread
- VM Mirror now caches the most part of mirrors objects (longlive)
- other mirrors own only ids and ask vm to give associated object
- reply packet error code check
- method mirror - resolves #12
- module mirror - resolves #11
- breakpoints events - resolves #9
- code style improvements