Add utility functions for using the Hammer IO system (#1530)
Example usage
```lua
function ENT:KeyValue( key, value )
if ( BaseClass.KeyValue ) then BaseClass.KeyValue( self, key, value ) end
if ( self:SetNetworkKeyValue( key, value ) ) then
return
elseif ( self:AddOutputFromKeyValue( key, value ) ) then
return
end
-- Your entity's logic goes here
end
function ENT:AcceptInput( name, activator, called, value )
if ( BaseClass.AcceptInput and BaseClass.AcceptInput( self, name, activator, called, value ) ) then
return true
end
if ( self:AddOutputFromAcceptInput( name, value ) ) then
return true
end
-- Your entity's logic goes here
return false
end
```
