Dimcli

* Gsheets export shortcuts
* Export DSL results to gsheets: `DslDataset.to_gsheets()`
* CLI command: `.export_as_gsheets`
* `utils.export_as_gsheets` accepts both API JSON and (any) pd.DataFrame
* DSL grammar updated for version 1.28 (2020-09 release)
* Bug fix: json_normalize errors when creating
* Updated DSL grammar for dimcli CLI autocomplete
* fix bug caused by new `_copyright` in JSON response
* `to_json_file` replaces `DslDataset.save_json`

* DSL grammar updated for version 1.27 (2020-08 release)
* Refactoring of grammar objects
* Added methods to save/load JSON data from DslDataset object
* `DslDataset.load_json_file` (class method) and `DslDataset.save_json` (object method)
* `Dsl.query_iterative` takes an extra argument `maxlimit` forcing to stop the iteration when N results have been extracted

* Improve support for iterative queries using DSL `unnest` operator
* Time elapsed info

* DSL grammar updated for version 1.26 (2020-07 release)

* refactored functions wrappers location `dimcli.core.functions.*` but can be imported using `dimcli.shortcurts`

* `DslDataset.as_dataframe_concepts()` method: refactoring so to handle latest concept scores
* `shortcuts.extract_concepts` method: wrapper for DSL function
* `shortcuts.extract_classification` method: wrapper for DSL function
* `shortcuts.extract_grants` method: wrapper for DSL function