Filter Abstraction (#25)

* 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

SabreTools.Library/DatItems/Sample.cs

@@ -32,6 +32,7 @@ namespace SabreTools.Library.DatItems
 
                 Supported = this.Supported,
                 Publisher = this.Publisher,
+                Category = this.Category,
                 Infos = this.Infos,
                 PartName = this.PartName,
                 PartInterface = this.PartInterface,