Add --clean option to deploy script

Allows the deploy script to remove files in the target that are not preset
in the current repository. This patch assumes pure stock osTicket
deployments -or- that the files deployed in the target are also present in
the local repository.
Merge pull request #49 from greezybacon/feature/deploy-clean

Add --clean option to deploy script

Reviewed-By: Peter Rotich <peter@osticket.com>