Better federation algorithm

[coyotte508]

Know when to give up looking for federations.

With the following data: https://gist.github.com/coyotte508/3e431a5cf077808a63cc306b44e0708e

Ivits, when they convert power to a qic, trigger a refresh of the federation cache. And it causes the site to hang too long and causes an error 504 and they can't complete their next move.

At least, for ivits, planets that are unreachable from the current federation should be excluded from the search space.

More generally, if with a given number of satellites any two building groups can not be connected, the suggested federation should be discarded.

[coyotte508]

Addressed by 0e8acbc