Major refactor

MathEngine/MathRunner/Program.cs

@@ -0,0 +1,15 @@
+using MathEngine.Expression;
+
+namespace MathRunner
+{
+    internal class Program
+    {
+        static void Main(string[] args)
+        {
+            Console.WriteLine("Evaluting expression...");
+            Expression exp = new("54+2+1");
+            Console.WriteLine(exp.Evaluate());
+            Console.WriteLine("Hello, World!");
+        }
+    }
+}