This has the added benefit of clearing out a lot of boilerplate for new DatItem types, since DiskArea only pertains to the Disk type and DataArea only pertains to the Rom type
* Add category, back filters by dictionary
* Complete internal filter set
* Fix AreaSize filter
* Populate filter object the hard way
* Manipulation flags should not be filters
* None of them need to be public
* Convert to partial helper method
* Better method use
* Field, not string; no dictionary
* Add FilterTo method for later
* More naming options (easier conversion)
* Update README
* Syntax cleanup
* More minor cleanup, use Linq
* Fix broken features by using correct values
* Feature flags the same
* Features are modular
* No AlphaFS, more .NET versions
* Fix appveyor
* Put back identifiers, for some reason
* String interpolation, modernization
* Better use of GetField
* XmlTextWriter to remove possible issues
* Fix header for OpenMSX