Variable size facilities

**What do you want to see?**
Facilities that are not necessarily the same size, like in SE5. As suggested by bearclaw.

**How would it help players?**
You could have different sizes of space yards with different rates, or a cost vs. space tradeoff for mineral miners, or whatever you want...

**Alternatives**
N/A

**Screenshots and mockups**
N/A

**Things to consider**
Should we use integers or doubles or decimals to represent facility size? Should the default facility size be 1 or 1000 or something else? Probably 1 to avoid breaking PlanetSize.txt.