- Moves DimExtractionFn under a more generic ExtractionFn interface to
support extracting dimension values other than strings
- pushes down extractionFn to the storage adapter from query engine
- 'dimExtractionFn' parameter has been deprecated in favor of 'extractionFn'
- adds a TimeFormatExtractionFn, allowing to project the '__time' dimension
- JavascriptDimExtractionFn renamed to JavascriptExtractionFn, adding
support for any dimension value types that map directly to Javascript
- update documentation for time column extraction and related changes