[Feature Request] Add columns to Coin table to make Imports easier

[andyrozman]

I think we need to add SOURCE_TYPE and SOURCE_ID columns to main Coin table (they should be there always, not dynamic like all other fields seem to be (which is bad idead anyways, especially if you reconfigure everything aftwards). So when we imports either from Colnect or Numismatic we set this values, so that next time when we import, we wouldn't import this item again (unless we really want to).