Add "poweredgriddistancegreaterthan" cleanup filter.

[FerrenF]

This PR introduces a condition implementation for grids which are nearby another grid that is powered (excluding itself): "poweredgriddistancegreaterthan". On the server this was made for, cleanup conditions include:

"Must not have 'Grid' in the name"
"Must not have the starter ship name"
"Must have a beacon"

Grids not matching all of these conditions are removed. This can lead to some rather unfortunate situations with players starting builds at their base at the wrong time or with looting wrecks. A condition that checks for nearby powered grids would go significant lengths towards reducing the amount of 'oopsie' player grid deletions.

Let the roast begin... ?

[StalkR]

Basically: we can use the existing condition nopower to find and cleanup all unpowered grids, but we want to avoid cleaning up the unpowered grids (e.g. rover) at your (powered) base grid. This is the condition that implements it: clean up all the unpowered grids but only the ones that are all alone. Thanks for your consideration!