Exclude geography/datasource combinations

[avmey]

Some datasources don't need to be precalculated against every geography (for example, needing to precalc for a specific subregion only). Currently, we precalculated each datasource by each geography.

• Add precalcGeographies property to datasources that is a whitelist of geographies to precalculate for. Support default or all
• Enhance precalc:data:cleanup to support filtering out stale ds/geog combinations no longer needed
• When user import:data it asks “Which geographies would you like to precalculate metrics for?” (select list with all geographies and ‘all’ options is selected by default)

Medium priority.