Add and use BSP constants

BurnOutSharp.Models/BSP/Constants.cs

@@ -0,0 +1,25 @@
+namespace BurnOutSharp.Models.BSP
+{
+    public static class Constants
+    {
+        /// <summary>
+        /// Number of lumps in a BSP
+        /// </summary>
+        public const int HL_BSP_LUMP_COUNT = 15;
+
+        /// <summary>
+        /// Index for the entities lump
+        /// </summary>
+        public const int HL_BSP_LUMP_ENTITIES = 0;
+
+        /// <summary>
+        /// Index for the texture data lump
+        /// </summary>
+        public const int HL_BSP_LUMP_TEXTUREDATA = 2;
+
+        /// <summary>
+        /// Number of valid mipmap levels
+        /// </summary>
+        public const int HL_BSP_MIPMAP_COUNT = 4;
+    }
+}