Implement hourly compaction

[Jaana Dogan]

Data points should be compacted into hourly aggregations and be written to a new table called compact_events. When querying we query the compact events first and merge them with the rows from events. Querying request should take a StartTime argument to limit the querying to a specific time window or use a default (e.g. last 7 days) if the user hasn't set one.