This commit adds incoming and outgoing channel ids filter to forwarding history request to filter events received/forwarded from/to a particular channel
We use the event timestamp of a forwarding event as its primary storage
key. On systems with a bad clock resolution this can lead to collisions
of the events if some of the timestamps are identical. We fix this
problem by shifting the timestamps on the nanosecond level until only
unique values remain.
This commit moves makeTestDB to db.go and exports it so that we'll be
able to use this function in other unit tests to make them testable with
etcd if needed.
