Cubejs Playground App should have select column option and set title

**Is your feature request related to a problem? Please describe.**
This change request related to make simplier UX for BI consultation when the task is create on existing complex datasource a smart CubeJS. So when i start to create a new schema I have option A. generate a schema B. create manually. When I generate it the system generates each columns found in source table so I need open schema then remove each unnecessary columns/dimensions. However when i create from scratch i should make some mistakes and find columns from source db - both takes too much time. Really frustrate me.

Use Case: I assume I have postgres includes 60 columns, however the output require only 10 dimensions. BI Consultant would like select columns to be converted into schema dimensions.

**Describe the solution you'd like**
As simple and powerful solution would be improve schema generation by adding in right pane a "table" list all fields including fieldtypes and title column. tasks
1. admin/biconsultant select table in left pane (fields and table listed)
2. Consultant select fields by checkbox - as candidates to be converted into dimension
3. Set titles for dimensions.
4. click on Generate Scheme (cubejs generate new schema excluding fields and set titles)

**Describe alternatives you've considered**
probably later some filters for column - filter as type- should speed up select each right columns.

**Additional context**