Factoring & new functionnality

factoring code

    * read config from common.conf for Zps.pm fix #1
    * read config from common.conf for Rsync.pm fix #1
    * read timezone from common.conf fix #2

New functionnality

    * gzb_make_snapshot.pl : make first snapshot if no snapshot found
    * gzb_send_snapshot_to_remote.pl : full send if no remote snapshot found