split instruction into software installation and import

Basically leaves the part that needs to be done by the automatic
vagrant script in the bash script and moves the remaining part
into an OS-independent md file.

Also fixes some of the instructions for CentOS. Now almost runs
through (some minor issue with permission remains).

docs/bash2md.sh

@@ -0,0 +1,7 @@
+#!/bin/sh
+#
+# Extract markdown-formatted documentation from a source file
+#
+# Usage: bash2md.sh <infile> <outfile>
+
+sed '/^#!/d;s:^#\( \|$\)::;s/.*#DOCS://' $1 > $2