fixed gc overhead limit in chord
Merge pull request #257 from ambiata/fix-chord

fixed gc limit bug in chord
Remove unused NotImplemented.generate
removed "hole in the middle" funtion when ingesting facts
added the snapshot id to the SnapshotMeta class
removed the hole-in-the-middle for snapshots
cleaned-up the chord code
using as(x) instead of .map(_ => x)
merged with master
fixed the failing test and added the -Ywarn-value-discard flag
split the ingest logic to allow the use of a different importer
use the downcast method for checking the repository type and downcast it
fixed the logic for taking a snapshot incrementally
merged with master
added the -Yno-adapted-args flag
added a property for checking if the latest snapshot is up to date
fixed the Chord code to get the latest snapshot when extracting a Chord
added a spec for Entities
fixed the logic for defining if a snapshot is up to date or not
fixed compilation errors after the rebase