Added generic typing to layer properties and keyframes

Restructured the way property input VMs are created

src/Artemis.Core/Models/Profile/LayerProperties/BaseLayerProperty.cs

@@ -0,0 +1,98 @@
+using System;
+using System.Collections.Generic;
+using Artemis.Core.Exceptions;
+
+namespace Artemis.Core.Models.Profile.LayerProperties
+{
+    public abstract class BaseLayerProperty
+    {
+        private object _baseValue;
+
+        protected BaseLayerProperty(Layer layer, BaseLayerProperty parent, string id, string name, string description, Type type)
+        {
+            Layer = layer;
+            Parent = parent;
+            Id = id;
+            Name = name;
+            Description = description;
+            Type = type;
+
+            Children = new List<BaseLayerProperty>();
+            BaseKeyframes = new List<BaseKeyframe>();
+        }
+
+        /// <summary>
+        ///     The layer this property applies to
+        /// </summary>
+        public Layer Layer { get; }
+
+        /// <summary>
+        ///     The parent property of this property.
+        /// </summary>
+        public BaseLayerProperty Parent { get; }
+
+        /// <summary>
+        ///     The child properties of this property.
+        ///     <remarks>If the layer has children it cannot contain a value or keyframes.</remarks>
+        /// </summary>
+        public List<BaseLayerProperty> Children { get; set; }
+
+        /// <summary>
+        ///     A unique identifier for this property, a layer may not contain two properties with the same ID.
+        /// </summary>
+        public string Id { get; set; }
+
+        /// <summary>
+        ///     The user-friendly name for this property, shown in the UI.
+        /// </summary>
+        public string Name { get; set; }
+
+        /// <summary>
+        ///     The user-friendly description for this property, shown in the UI.
+        /// </summary>
+        public string Description { get; set; }
+
+        /// <summary>
+        ///     An optional input prefix to show before input elements in the UI.
+        /// </summary>
+        public string InputPrefix { get; set; }
+
+        /// <summary>
+        ///     An optional input affix to show behind input elements in the UI.
+        /// </summary>
+        public string InputAffix { get; set; }
+
+        /// <summary>
+        ///     The type of value this layer property contains.
+        /// </summary>
+        public Type Type { get; set; }
+
+        protected List<BaseKeyframe> BaseKeyframes { get; set; }
+        /// <summary>
+        ///     A list of keyframes defining different values of the property in time, this list contains the untyped <see cref="BaseKeyframe"/>.
+        /// </summary>
+        public IReadOnlyCollection<BaseKeyframe> UntypedKeyframes => BaseKeyframes.AsReadOnly();
+
+        protected object BaseValue
+        {
+            get => _baseValue;
+            set
+            {
+                if (value != null && value.GetType() != Type)
+                    throw new ArtemisCoreException($"Cannot set value of type {value.GetType()} on property {this}, expected type is {Type}.");
+                _baseValue = value;
+            }
+        }
+
+
+        public void ApplyToEntity()
+        {
+            // Big o' TODO
+        }
+
+        public override string ToString()
+        {
+            return $"{nameof(Id)}: {Id}, {nameof(Name)}: {Name}, {nameof(Description)}: {Description}";
+        }
+    }
+}