[Toaster] toaster-manual: Explain the local release

[Barros Pena, Belen]

This branch

http://git.yoctoproject.org/cgit/cgit.cgi/poky-contrib/log/?h=bbarrosp/toas
ter/9229

Includes a patch to add an explanation of the local release to the Toaster
manual

a15de52894aeb7acf6a96404b2e56d314643f005
toaster-manual: Explain the local release

The fact that the Local Yocto Project release does not provide any
compatible layers confuses people. Add a section about the local release
to explain what it does.

[YOCTO #9229]

The patch includes a few new .png files to illustrate the content.

Thanks!

Belén