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/DatItem.cs

@@ -206,6 +206,32 @@ namespace SabreTools.Library.DatItems
             }
         }
 
+        /// <summary>
+        /// Machine category, if available
+        /// </summary>
+        [JsonIgnore]
+        public string Category
+        {
+            get
+            {
+                if (_machine == null)
+                {
+                    _machine = new Machine();
+                }
+
+                return _machine.Category;
+            }
+            set
+            {
+                if (_machine == null)
+                {
+                    _machine = new Machine();
+                }
+
+                _machine.Category = value;
+            }
+        }
+
         /// <summary>
         /// Machine romof parent
         /// </summary>
@@ -633,6 +659,9 @@ namespace SabreTools.Library.DatItems
                 case Field.Publisher:
                     fieldValue = this.Publisher;
                     break;
+                case Field.Category:
+                    fieldValue = this.Category;
+                    break;
                 case Field.RomOf:
                     fieldValue = this.RomOf;
                     break;