(WIP) Events

Todo:
- [x] Read events from the user command response
- [x] Read events from the message stream
- [x] Make a loop to do longpolling/shortpolling
- [x] Replace std:cerr by exceptions
- [x] mutex
Yes, it's supported by all the compilers now.

Pros:
* syntax
Cons:
* non standard

Moreover, we are trying to follow the google c++ style guide (I think they do more c++ than us, and they are probably smarter on this subject), and they are talking about `include` guard, but nothing about `#pragma once` http://google-styleguide.googlecode.com/svn/trunk/cppguide.xml#The__define_Guard.

Tbh, I never used this instruction by the past, and never had to change some code from an application which uses it.

If there is a request, the question can be discussed, but I won't change it, if you are the only one who suggest to change it.