Add BiDictionary data type and its simple unity tests

* Modify the structure a bit so the project will be more maintainable
* Add unit test support
* Clean up the package dependencies

.gitignore

@@ -187,7 +187,7 @@ PublishScripts/
 # NuGet Packages
 *.nupkg
 # The packages folder can be ignored because of Package Restore
-**/packages/*
+# **/packages/*
 # except build/, which is used as an MSBuild target.
 !**/packages/build/
 # Uncomment if necessary however generally it will be regenerated when needed

Assets/DataStructures/BiDictionary/BiDictionary.cs

@@ -0,0 +1,76 @@
+using System.Collections;
+using System.Collections.Generic;
+
+namespace DataStructures.BiDictionary
+{
+    public class BiDictionary<TKey, TValue> : IBiDictionary<TKey, TValue>
+    {
+        private readonly Dictionary<TKey, TValue> forward = new Dictionary<TKey, TValue>();
+        private readonly Dictionary<TValue, TKey> reverse = new Dictionary<TValue, TKey>();
+
+        public BiDictionary()
+        {
+            KeyMap = forward;
+            ValueMap = reverse;
+        }
+
+        public Dictionary<TKey, TValue> KeyMap { get; private set; }
+        public Dictionary<TValue, TKey> ValueMap { get; private set; }
+
+        public int Count() => forward.Count;
+
+        public void Add(TKey key, TValue value)
+        {
+            if (key != null && value != null)
+            {
+                forward.Add(key, value);
+                reverse.Add(value, key);
+            }
+        }
+
+        public bool ContainsKey(TKey key)
+        {
+            return forward.ContainsKey(key);
+        }
+
+        public bool ContainsValue(TValue value)
+        {
+            return reverse.ContainsKey(value);
+        }
+
+        public bool RemoveKey(TKey key)
+        {
+            var value = forward[key];
+            return value != null && reverse.ContainsKey(value)
+                && reverse.Remove(value) && forward.Remove(key);
+        }
+
+        public bool RemoveValue(TValue value)
+        {
+            var key = reverse[value];
+            return key != null && forward.ContainsKey(key)
+                && forward.Remove(key) && reverse.Remove(value);
+        }
+
+        public IEnumerator<KeyValuePair<TValue, TKey>> GetValueEnumerator()
+        {
+            return reverse.GetEnumerator();
+        }
+
+        public IEnumerator<KeyValuePair<TKey, TValue>> GetEnumerator()
+        {
+            return forward.GetEnumerator();
+        }
+
+        IEnumerator IEnumerable.GetEnumerator()
+        {
+            return forward.GetEnumerator();
+        }
+
+        public void Clear()
+        {
+            forward.Clear();
+            reverse.Clear();
+        }
+    }
+}

Assets/DataStructures/BiDictionary/IBiDictionary.cs

@@ -0,0 +1,20 @@
+using System.Collections.Generic;
+
+namespace DataStructures.BiDictionary
+{
+    public interface IBiDictionary<TKey, TValue> : IEnumerable<KeyValuePair<TKey, TValue>>
+    {
+        Dictionary<TKey, TValue> KeyMap { get; }
+        Dictionary<TValue, TKey> ValueMap { get; }
+
+        void Add(TKey key, TValue value);
+        void Clear();
+        bool ContainsKey(TKey key);
+        bool ContainsValue(TValue value);
+        int Count();
+        new IEnumerator<KeyValuePair<TKey, TValue>> GetEnumerator();
+        IEnumerator<KeyValuePair<TValue, TKey>> GetValueEnumerator();
+        bool RemoveKey(TKey key);
+        bool RemoveValue(TValue value);
+    }
+}

Assets/DataStructures/DSUnity.asmdef

@@ -0,0 +1,3 @@
+{
+	"name": "DSUnity"
+}