[drupal-docs] install guide on the database config

[Anisa]

I remember thinking once it would be nice to have drupal share a 
database with another cms install on my site, so I tried to change the 
database prefix in the config file, and followed the instructions in the 
install.txt, but came up with mysql errors that were only fixed when I 
removed the database prefix from the config file.

I do not know how to make this better, but somehow I don't think 
uploading the config file first will do anything if you don't change the 
database.mysql file either (a la http://drupal.org/node/2622).  There is 
no mention of that in the config file nor the install text.  At least, 
not that I saw.

Anisa.