Planetary Stations Update 1.5.2

Before starting work on the Real Space update, I decided to add what I
didn't have time to do in the previous big update for Planetary Stations.
Basically these are just graphical changes for the hot giant and the scorched
world, but it took me a while. I hope you appreciate the result.

Due to some quirks of the code, hot giant is now a full-fledged planet
class. You will also now see a mention that only barren worlds can be cracked.
(There have been many questions about this.)