Analytic unit metric selection

[rozetko]

You can have multiple metrics from 1 query, but multiple metrics are not supported yet We should add metric Select for each analytic unit

[rozetko]

Pitfalls

• there is no obvious way to bind metric queries to their responses. Response doesn't contain any identification
• there is no obvious way to bind original metric names to their aliases. Datasources set aliases without adding them to the query