Use AutoExecConfig library for core convars

New convars will be added to the existing config file.
Added adminflags parameter to RegisterUpgradeType

Plugins can now set the default required adminflags for their upgrade.
Added central config to disable visual effects

Upgrades can tell the core if they plan to run visual and/or sound
effects on clients. The core creates convars and lets the serveradmin
decide if the cosmetical effects should be played.
Update upgrades to use new RegisterUpgradeType
Obey cosmetical effect settings in upgrades