Another major reworking of our pull system.
Another major reworking of our pull system.

Now it's so fast we're CPU bound by the old version of EarthFS we're pulling from, but we have a hack of not checking for duplicates before importing each file because we can't read the database while it's being written. Sounds like a job for the write-ahead log.

nkatsaros/stronglink,Lacra17/stronglink,feld/stronglink,rmoorman/stronglink,Ryezhang/stronglink,btrask/stronglink,yamingd/stronglink,btrask/stronglink,shaunstanislaus/stronglink,shaunstanislaus/stronglink,btrask/stronglink,rmoorman/stronglink,yamingd/stronglink,Lacra17/stronglink,iOSCowboy/stronglink,guiquanz/stronglink,guiquanz/stronglink,guiquanz/stronglink,nkatsaros/stronglink,iOSCowboy/stronglink,Ryezhang/stronglink,feld/stronglink,iOSCowboy/stronglink,shaunstanislaus/stronglink,btrask/stronglink,yamingd/stronglink,feld/stronglink,nkatsaros/stronglink,Lacra17/stronglink,Ryezhang/stronglink,rmoorman/stronglink