Display conditions - Added basic models

Display conditions - Added externally registerable condition operators
Display conditions - Added GreaterThan condition for testing

src/Artemis.Core/Services/Interfaces/IDataModelService.cs

@@ -1,7 +1,9 @@
 using System.Collections.ObjectModel;
-using Artemis.Core.Models;
+using Artemis.Core.Annotations;
+using Artemis.Core.Models.Profile.Conditions;
 using Artemis.Core.Plugins.Abstract;
 using Artemis.Core.Plugins.Abstract.DataModels;
+using Artemis.Core.Plugins.Models;
 
 namespace Artemis.Core.Services.Interfaces
 {
@@ -22,9 +24,22 @@ namespace Artemis.Core.Services.Interfaces
         void RemoveExpansion(DataModel baseDataModelExpansion);
 
         /// <summary>
-        /// If found, returns the data model of the provided plugin
+        ///     If found, returns the data model of the provided plugin
         /// </summary>
         /// <param name="plugin">Should be a module with a data model or a data model expansion</param>
         DataModel GetPluginDataModel(Plugin plugin);
+
+        /// <summary>
+        ///     Registers a new condition operator for use in layer conditions
+        /// </summary>
+        /// <param name="pluginInfo">The PluginInfo of the plugin this condition operator belongs to</param>
+        /// <param name="layerConditionOperator">The condition operator to register</param>
+        void RegisterConditionOperator([NotNull] PluginInfo pluginInfo, [NotNull] LayerConditionOperator layerConditionOperator);
+
+        /// <summary>
+        ///     Removes a condition operator so it is no longer available for use in layer conditions
+        /// </summary>
+        /// <param name="layerConditionOperator">The layer condition operator to remove</param>
+        void RemoveConditionOperator([NotNull] LayerConditionOperator layerConditionOperator);
     }
 }