Use a pre-build script to generate usage.h from the README.md

Use a generated header from README.md
Finalise git ignore file

source/scripts/gen_usage.sh

@@ -0,0 +1,9 @@
+#! /bin/bash
+# Used to generate usage text from markdown
+cat README.md                        \
+    | sed 's/^#* //g'                \
+    | sed 's/\t/\\t/g'               \
+    | sed ':a;N;$!ba;s/\n/\\n\n/g'   \
+    | sed 's/^/\"/'                  \
+    | sed 's/$/\"/'                  \
+    > $1