XML file changes: dropping .driver.xml

[Andrus Adamchik]

Since I am rewriting the project load/save code, I am going to add one  
more format change - move .driver.xml stuff into cayenne.xml. The  
original motivation for a separate file was to allow users to swap it  
in different deployment environments, e.g. to protect their production  
password. Now we have the password encoder facility that does not  
require file swapping, and most JEE environments are using JNDI  
anyways, so makes sense to reduce the complexity, and store the  
<driver>..</driver> section right in cayenne.xml.

Andrus