Created Unassigned: ExcelDataValidationType.None not implemented [15528]

DataValidations fails with the following error:
"Invalid schemaname: none"

This Fails:
var DataValidation = ws.DataValidations;

Because ExcelDataValidationType.None is not yet implemented, but should be:
```
Custom Data validation which use a custom formula to check the cell value.
Date Data validation which checks for date values satisfying the given condition.
Decimal Data validation which checks for decimal values satisfying the given condition.
List Data validation which checks for a value matching one of list of values.
None Allows any type of value and does not check for a type or range of value.
TextLength Data validation which checks for text values, whose length satisfies the given condition.
Time Data validation which checks for time values satisfying the given condition.
Whole Data validation which checks for whole number values satisfying the given condition.
```