[Vodyani] Toggle planet exploitation (small QoL improvement)

Now that the latest colonization tech are available, I feel the Vodyani could use a small quality of life improvement: the ability to toggle the exploitation of a planet, i.e. the ability to choose to not exploit a planet.

Problem: Unlocking advanced colonization tech can feel detrimental as a Vodyani player

Problem 2: Late game a new Ark colonizing a new system might have heavy unhappiness issues since it lacks any happiness related building but exploits planets with heavy modifiers. Other empires don't have this issue since they can colonize the system progressively.

Cause: Some planet have heavy unhappiness modifier attached to them. In particular Gas Giant or some planet with multiple negative anomaly. Also the Vodyani lack the capacity to terraform or remove anomaly.

Proposed solution: Let the player be able to choose not to exploit a planet.

Effect of the solution: If a planet isn't exploited, it provide no FIDSI (loss) but also no unhappiness (win). Exploiting a planet becomes a meaningful choice even if in most case the best choice is to exploit the system fully. Also advanced colonization tech don t become a potential liability. Finally it would make sense: why would a system keep exploiting 4 Gas Giant and be unhappy if they could be happy exploiting only 2.

Form of the solution: A small toggle button in the system view under each colonizable planet. Active by default, when inactive the planet isn't exploited