[JourneyMap] Persistent vein beam

[TheElan]

Steps to reproduce:

1. double click the vein to activate beam
2. Re-start the game
3. Observe vein not being selected anymore

I usually use this feature of JM to mark where my miners at. Would be nice to have it.

[PolkageistHS]

Also one stupid-tiny request if you're touching the marker: could it be at 7,7 in the chunk instead of 8,8? That way it matches up with the InGameInfoXML "You are in the center of the chunk" thingy.