Clean out and archive legacy code

[pmpowers-usgs]

Anything that is a dependency will be migrated elsewhere.

• src/org.opensha.gem (also org.opensha.sha... files) (Gem clean #23)
• src/org.opensha.nshmp2
• src/scratch/bbradley (Dev scratch cleaning #19)
• src/scratch/christine (Dev scratch cleaning #18)
• src/scratch/datamind (Dev scratch cleaning #18)
• src/scratch/jennie (Dev scratch cleaning #18)
• src/scratch/marco (Dev scratch cleaning #18)
• src/scratch/martinez (Dev scratch cleaning #19)
• src/scratch/olsen (Dev scratch cleaning #18)
• src/scratch/peter
• src/scratch/ramses (Dev scratch cleaning #18)
• src/scratch/vipin (Dev scratch cleaning #18)