Minor fixups to zonelist handling

These are minor enhancements needed to the zonelist handling:

1) Add a confirmation step to both 'ods-enforcer zonelist import' and 'ods-enforcer update zonelist' that says:
"This will overwrite the contents of the database with the contents of zonelist.xml. The zonelist.xml file may be out of sync with the database - please check the contents carefully. Do you want to proceed?"
2) Add a '--force' option to the same two commands to have the user bypass this confirmation
3) Need to create a zonelist.backup file when updating it on 'ods-enforcer zone add/delete --xml' as is done in 1.4. This should be done by implementing a low level copy method (currently only a cp using a system call is available in 2.0).
4) We need to look at how trailing dots in the zone names are handled. There is special handling for this in 1.4 that we should try to understand and then reproduce
5) Also need to double check how/if keys are cleaned up when zones are deleted in 2.0
6) Also review if there should be an xml version header output when xml is streamed to a socket (it is there when output to a file).