Summary:
Handle reference columns in ViewFieldRec.valueParser.
Extracted code for reuse from ReferenceEditor to look up values in the visible column. While I was at it, also extracted a bit of common code from ReferenceEditor and ReferenceListEditor into a new class ReferenceUtils. More refactoring could be done in this area but it's out of scope.
Changed NTextEditor to use field.valueParser, which affects numeric and reference fields. In particular this means numbers are parsed on data entry, it doesn't change anything for references.
Test Plan:
Added more CopyPaste testing to test references.
Tested entering slightly formatted numbers in NumberFormatting.
Reviewers: dsagal
Reviewed By: dsagal
Differential Revision: https://phab.getgrist.com/D3094
