New behavior to edit some existing config.xml rather than generating from scratch

New behavior is now to exportsystemconfiguration from the server, and then edit the config.xml that is received from that.  
If config_xml is passed in (in the case of clone), that config.xml will be used instead of exporting.

NOTE: I have not been able to test to ensure VMs are working.  It seems there are other changes being made in asm-deployer and asm-core that might be affecting this.  I don't know what could fail due to a server/host being configured incorrectly, but may want to wait to merge these changes untl I can confirm that's working.