Change folder hierarchy
Update include paths
Add scheduler
Add FakeSystem for demo
Enable multithreading in gcc
Fix argument of functor
Revert commit d40b0592e9abc3a3122ea145237ca26178b57166
Add multithread flag to gcc
Cut lines to 80/120 cols
Remove thread_local storage
Merge remote-tracking branch 'origin/develop' into feature-scheduler

Conflicts:
	src/main.cpp
Add GLFW OS instance to TrillekGame
Use GLFW time function as clock and implement a global terminate flag
Replace steady_clock::now() calls by GLFW timer in header
OS loop is managed by the scheduler.

The main thread is blocked in a loop, waiting the window to be closed.
The terminate flag has been replaced by a call to OS::Closing().
Manage termination of the program
Systems have a Terminate() function called when the program exits
Add some comments
Remove all steady_clock reference as workaround of MSVC bug
Remove tests that are specific to the c++ library used