Add mode $8800 tilemap conversion tool

src/tools/bit7ify.py

@@ -0,0 +1,8 @@
+#!/usr/bin/env python3
+
+from sys import argv
+
+
+with open(argv[1], "rb") as input:
+    with open(argv[2], "wb") as output:    
+        output.write(bytes((byte ^ 0x80  for byte in input.read())))