update instructions for install fmon on kobos

If a user install fmon first and then extract  all the contents of the zip  (the koreader folder and KoboRoot.tgz under .kobo/ and koreader.png in main folder) together, we reach some CRITICAL condition:

1 koboroot.tgz triggers an update BEFORE indexing koreader.png in the database
2 the update triggers a reboot which launchs fmon with the koreader script associated to koreader.png
3 nickel find a new valid file and start indexing, this trigger koreader.sh (file koreader.png was opened)
4 koreader.sh kills nickel, the koreader.png image is not indexed. 
5 at koreader exit we launch nickel again, but we back to 3

When we reach this critical condition:
- the reader will boot directly to koreader
- the reader will start koreader again at koreader exit

I think is a good idea to copy the image first, even before install fmon, And just follow next steps if we are able to find koreader.png in kobo library.

Any thoughts?