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/DatFiles/SeparatedValue.cs

@@ -213,6 +213,10 @@ namespace SabreTools.Library.DatFiles
                             machine.Publisher = value;
                             break;
 
+                        case "Machine.Category":
+                            machine.Category = value;
+                            break;
+
                         case "Machine.RomOf":
                             machine.RomOf = value;
                             break;