Added Parser

- can parse a basic token list to an AST

Compiler/Parser/Nodes/ConstantNode.cs

@@ -0,0 +1,14 @@
+namespace Compiler.Parser.Nodes
+{
+    public sealed class ConstantNode : Node
+    {
+        public override NodeType NodeType { get; set; }
+        public int value { get; set; }
+
+        public ConstantNode(int value)
+        {
+            this.NodeType = NodeType.ExpressionNode;
+            this.value = value;
+        }
+    }
+}