parameterless constructor

Commit #16's parameterless constructor is not in the source code anymore. Is there a reason for this?

In order to put the smartEnum into a EF Core Table, now I need to do the following for the constructor
```
// base("default", "default") should not be needed. and it adds confusion for programmer I think.
protected BaseOptionType() : base("default", "default")
{
IsRequired = false;
}
```
[EF Core Value Conversions](https://github.com/ardalis/SmartEnum#persisting-with-ef-core-21-or-higher) does not work for me, because I do want to save both name and value into the database, so user can add record to it later as well.

related issues
#16
#15

Start by reviewing related issues #16 and #15 and the linked EF Core Value Conversions documentation. Determine how SmartEnum persistence should support storing both name and value without the workaround constructor; done means the requested parameterless-constructor behavior is supported and covered by appropriate tests.

Written by the indexing model from the issue text.