Improving client-server experience

[ScriptedSnark]

Some of these tasks can be incompatible with other clients including vanilla.

• [ ] Custom HUD element (something like CHudCustom from Sven Co-op)
• [ ] Progressbar like in Counter-Strike 1.6
• [ ] Timer HUD
• [ ] Customizable deathnotice message
• [x] Health usermessage, HUD which supports >999 HP
• [ ] Extended ammo counter, weapon selection HUD (slots/positions)
• [x] env_fog
• [ ] Increase MAX_WEAPONS to 64
• [ ] Add "ViewModel" usermessage: https://github.com/ValveSoftware/halflife/issues/199
• [ ] Increase HUD channels limit: https://github.com/ValveSoftware/halflife/issues/1988