Summary:
- Normally Reference columns can only be used for data entry once the target
table has loaded. When it shows RowID, we shouldn't need to wait.
- Also, fix pasting values between cells of a RowID-showing column.
Test Plan: Added a test for entering data before data has loaded.
Reviewers: paulfitz
Reviewed By: paulfitz
Differential Revision: https://phab.getgrist.com/D2902