Integration of js-ipfs-repo-migrations brings automatic repo migrations
to ipfs-repo (both in-browser and fs). It is possible to control the
automatic migration using either config's setting
'repoDisableAutoMigration' or IPFSRepo's option 'disableAutoMigration'.

BREAKING CHANGE: repo.blocks.query() now returns multihashes as a key
instead of CID. If you want to have CID returned call it as query({},
true), which will constructs CIDv1 using IPLD's RAW codec. This means
that this constructed CID might not equal to the one that the block was originally
saved. Related to ipfs/js-ipfs#2415

Co-authored-by: achingbrain <alex@achingbrain.net>

…h_keys_in_datastore