Concealability per-turret without addon #458

Since #442 has been closed, and there is now a config setting to conceal all turrets without requiring the addon, I would like the functionality of this to be changed.

When the addon is not required, there should be a way for users to set whether the turret will conceal or not. This should be per-turret, not global as it currently is. We've discussed the possibilities of using a GUI button or the omlib wrench multitool to allow users to configure this setting.