Export analytic units

[rozetko]

This PR partially implements #830: adds an endpoint for exporting analytic units.

Changes

• new GET /panels/template endpoint which returns:
  • analytic unit templates (analytic units with some fields changed to variables)
  • analytic unit caches
  • segments
  • detection spans
• new types for serialized analytic units
• findMany method for AnalyticUnitCache
• findByAnalyticUnitIds method for DetectionSpans and Segments

Notes

We use TypeScript v2.6.8 which lacks "Omit" type from TS 3.5.1. This PR adds this type to server/src/types.ts, we can remove it when we'll update TS.

[jonyrock-back]

what is "analytic unit template" and why did you make it?

[rozetko]

@jonyrock-back "analytic unit template" is analytic unit config with some fields changed to variables, e.g.:

• panel ID
• grafana URL
• datasource URL

It's made for using same analytic units in different Hastic instances or dashboards