Breath is now handled server side. Changing this behaviour required some modifications to core:
* Ignore TOSERVER_BREATH package, marking it as obsolete
* Clients doesn't send the breath to server anymore
* Use PlayerSAO pointer instead of peer_id in Server::SendPlayerBreath to prevent a useless lookup (little perf gain)
* drop a useless static_cast in emergePlayer
PlayerSAO::disconnected() function was historical and remove the link between SAO and RemotePlayer session. With previous attributes linked to RemotePlayer saving was working. But now attributes are read from SAO not RemotePlayer and the current serialize function verify SAO exists to save the player attributes.
Because PlayerSAO::disconnected marks playersao for removal, only mark playerSAO for removal and let PlayerSAO::removingFromEnvironment do the correct saving behaviour and all the disconnection process instead of doing a partial removal and let the server loop doing the RemotePlayer cleanup and remove some saved attributes...
* Create UnitSAO, a common part between PlayerSAO & LuaEntitySAO
* Move breath to PlayerSAO & LocalPlayer
* Migrate m_yaw from (Remote)Player & LuaEntitySAO to UnitSAO
* Migrate m_yaw from Player to LocalPlayer for client
* Move some functions outside of player class to PlayerSAO/RemotePlayer or LocalPlayer depending on which class needs it
* Move pitch to LocalPlayer & PlayerSAO
* Move m_position from Player to LocalPlayer
* Move camera_barely_in_ceiling to LocalPlayer as it's used only there
* use PlayerSAO::m_base_position for Server side positions
* remove a unused variable
* ServerActiveObject::setPos now uses const ref
* use ServerEnv::loadPlayer unconditionnaly as it creates RemotePlayer only if it's not already loaded
* Move hp from Player to LocalPlayer
* Move m_hp from LuaEntitySAO to UnitSAO
* Use m_hp from PlayerSAO/UnitSAO instead of RemotePlayer
