With an example of Blink

And use more precise duration types

This avoids having to override them in subclasses even when the have nothing
to implement either

And clean some time-related stuf

fix #2268

ref #2268

Do not confuse with Screen::get_mouse_position()
(maybe find a different name…)

Should be a lot faster, since we look for components quite often, it should
be an important optimization

And fix the fog for that, as well

fix #2854

Use the Entity class everywhere, instead
fix #2803

mod/client_mode, and the action panels, mostly

fix #2855

We insert the new client in the list before. Otherwise a call to
“send_to_all_clients” would not include it

ref #2278