Provisioning model: please review my docs changes

[Bertrand Delacretaz]

Hi (Carsten mostly),

I made some small changes to the "model merging" section of
http://sling.apache.org/documentation/development/slingstart.html

Details at http://svn.apache.org/viewvc?view=revision&revision=1734922
- please cross-check.

-Bertrand