Xenoarchaeology update

Don't merge this yet, mapchanges still to come. Features include: 

- Major content overhaul and a bunch of new additions for xenoarchaeology.
- Digsites (strange rock deposits) are now much more nuanced and interesting, and a huge number of minor (non-artifact) finds have been added.
- Excavation is now a complex process that involves digging into the rock to the right depth.
- Chemical analysis is required for safe excavation of the digsites, in order to determine how best to extract the finds.
- Anomalous artifacts have been overhauled and many longstanding bugs with existing effects have been fixed - the anomaly utiliser should now work much more often.
- Numerous new artifact effects have been added and some new artifact types can be dug up from the asteroid.
- New tools and equipment have been added, including normal and spaceworthy versions of the anomaly suits, excavation tools and other neat gadgets.
- Five books have been written by subject matter experts from around the galaxy to help the crew of the Exodus come to grips with this exacting new science (over 3000 words of tutorials).