Fix bug: wrong directional constants

Assume you have a 2x2 sqare at (0; 0) and you want to enumerate it's
corners in form of Vector2 array. Those were wrong and were used in
Actor#GetOccupiedCells leading to incorrect collision detection and other
bugs.
Hide html body until page is loaded.
Improve error handling.
Tell Qt to use precise timer
Change way actors are deleted every tick

Only one actor was deleted, then it was "beak" out of cycle and here we go
to next tick. That's wrong, you have to collect dead actors in separate
array and process deletion.
Assure reindex actor after changing position

This was not done properly and introduced a lot of bugs.
Don't kill actors in "look". Don't ignore 'em here

Some types of actors were not sent in response to look request. And there
was a check of "health < 0 => kill it" for some unkown reason.
Fix bug: no BAD_ID for health < 0 actors
Rewrite a lot of web socket handling, it was buggy

Before third party WS lib was used and it could into threading. Then Qt
got native WS support and we switched to this only to find out it has no
threading support which is sad.