"No warp points" flag in SystemTypes.txt

**What do you want to see?**
A flag in SystemTypes.txt that disables warp point generation in a system.

**How would it help players?**
Modders could create special systems full of ruins or a ringworld or ultra rich planets or deadly monsters or whatever, and lock them behind warp manipulation tech.

**Alternatives**
N/A

**Screenshots and mockups**
N/A

**Things to consider**
FTL will screw with this, if I add it... also there is no way currently in SystemTypes.txt to specify a planet's resource value...