The upgrader determines schema and configuration customization by performing an ldif-diff of the base schema and configuration files with those in the current server.  Previously the invocation of this command just used the internal LDIFDiff class to perform this work.  Given the recent discovery of problems associated with using DirectoryServer in the same process when the filesystem bits and the jars are different version, this commit externalizes the command invocation to an external process using the currently installed jars.

I have created a new class ExternalTools for managing invocation of OpenDS tools in a different process, similar to what has been done with the ServerController.  In fact I have moved the backupDatabases method from ServerController to the new ExternalTools class since conceptually its not really about controlling the server.