CentOS 5/6 compatible back up rotation and more

Changelist:

- added auto qpress installation to installer
- Installer asks  for preferred backup time and configures a cron job
  under root's tab accordingly (full backup)
- rotate_backups function uses mtime instead of newermt (so it works
  on cent 5/6)
- for easy app manager integration full & inc actions spit out backup
  status to $backup/directory/backup.status:

status=0 after a successful run
status=1 after failure

I use a script monitor on fgo,, which checks the age of the
backup.status file (to make sure backups are running) and then use
app manager thresholds to alert if the file is stale or if it
contains status=1.

IMPORTANT:
Since rotate works differently, configuration file surrogate.conf
must be changed too:
instead of descriptive vars for retention, use days:

daily_retention="7"
weekly_retention="28"
monthly_retention="180"
Make qpress installation optional

Some environments may have qpress pre-installed through
other mechanisms such as package management.
Fixed retention settings in default config
Merge pull request #7 from comradeloren/sebas_rotation_fixes

Sebas rotation fixes