use updated sourmash core code more broadly

[bluegenes]

#134 makes necessary changes to allow us to use the new 0.12.0+ rust sourmash core.

With the new core, we can:

• Improve zip loading more broadly
  • Use core Collection and Manifest code --> standardize/improve zip and sigpath loading
• Standardize / improve selection
  • Use Collection::Select/Manifest::Select for subsetting when loading from zip
  • use Signature::Select to do selection and downsampling of single sigs