Restructure Changes

The following changes have been made in restructure logic:

During a restructure, the existing mappings will be preserved. The backend type of an existing column will remain the same after a restructure. This is independent of the configured mappings.
When creating new columns, the configured mappings will determine the backend type of the new columns.
The restructure process will now try to write a minimal INT file. In CK5, there would always be a Field_Length written to the INT file for Numeric, Date, Datetime, text, and binary type fields. This will now only be done if necessary. Only when the length of a column is different from the backend type, a length will be written.

The length of an integer is 9 positions. A numeric 9.0 column mapped to integer will not have a field length, while a numeric 8.0 column mapped to integer will have a length of 8 in the INT file.
Decimal types will never have a length in the INT file.
Date and datetime types will never have a length in the INT file.
Varchar(x) columns will not have lengths in the INT file.
Varchar(max) columns will have a length in the INT file because this type has no specific length on the backend.