More control over the maximum number of warp points in a system

**What do you want to see?**
There might be some setting which controls how many warp points can exist in a single star system. Whether or not there is, it needs to be available to configure at the mod level (Settings.txt), the game setup level, and the star system template level (SystemTypes.txt), with each item in the list overriding the previous or providing a default for the next.

**How would it help players?**
I think SE4 had a hardcoded limit of ten warp points per system; I'm not sure if FrEee has any limit. But looking at what players do with stellar manipulation, I've come to realize that a limit is actually a good thing. When players get SM tech, they tend to turtle up in a single system and open as many warp points as possible from that system coming from a single fortified sector; see #17 and #170 for other attempts to mitigate this cheesy tactic. If we just set the maximum number of warp points to five, excepting perhaps certain special systems (maybe black holes support fewer warp points because they're so massive and their gravity disrupts the warp lanes?) then that will not impact game setup since there are rarely more than five warp points per system anyway, but it will prevent some of the cheesy turtling tactics. Of course this will "give away" the location of black holes if say you try and fail to open a third warp point into them or whatever, but I think that's a reasonable thing for a knowledgeable player to surmise...

**Alternatives**
See the other issues linked above.

**Screenshots and mockups**
N/A

**Things to consider**
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