submodule glfw is now on the 3.0.4 branch

Working on master proved to be too unstable.
added glm 0.9.5 as a submodule
improved gl_service

- added „title“ constructor argument, which sets the window title
- added reshape callback which will be called when the framebuffer size
changes (this is also called once when calling gl_service::run())
- added mousedown/-up/-moved callbacks
- added scroll callback
- added gl_service::set_cursor_disabled(bool). passing true will hide
the cursor if the window is focused - pressing escape will show it
again and allow the user to regain control
- added gl_service::set_cursor_position(double,double)
- added time(), which returns the time since the first gl_service
instance was created