Is your feature request related to a problem? Please describe.
When importing data only the first row of data is used to infer the type of each of the columns in the datafile. This gives an issue when the first row contains a numeric value and the next a non-numeric value in the same column. This would help to enable importing data with object references (https://github.com/realm/realm-studio/issues/816).

Describe the solution you'd like
When having selected a data input file and a destination for my Realm I would like an overview of the resulting schema here each of the properties of the schemas are modifiable before the actual data import is performed.

Describe alternatives you've considered
None.

Additional context
See original issue https://github.com/realm/realm-studio/issues/790 and forum post https://forums.realm.io/t/is-it-possible-to-specify-a-field-type-for-csv-import-in-realm-studio/981