Removed code for never fixed feature.

The reason for remove is that code has been refactored and to implement
a similar feature one would have to take a different approach.
Added a lock for side controllers in mp::connect.

The lock is associated with "controller" attribute in SideWML.

The lock can be explicitly set by using a "lock_side_controllers"
attribute in ScenarioWML. If attribute won't be set, it would default to
"Use map settings" parameter.