Separate server & client settings

Client and server settings are mixed right now which makes it hard  to understand where you can use what. However the next change makes one more button for you to press to access your precious video settings, so it should be toggleable. Even while its disabled server settings you can't really change should be marked inactive (Simulation distance grayed out like difficulty).

Layout:

[Options...]
├ [Separate client/server] (toggle)
├ [Client options...]
│ ├ [Video settings...]
│ ├ [Language...]
│ └ [...]
│ [Server options...]
│ ├ [Difficulty: X | <Lock>]
│ ├ [Simulation Distance: XX]
│ ├ [Max Render Distance: XX] (The one in client is different, this sets how much is sent to client)
│ ├ [Game rules...]
│ └ [...]
└

Some server settings need to be in GUI though and this fits here very well. If server is ran externally, server options could be accessed by operators.