Updated for most recent toolkit version

- VM snapshots are now created before scheduling downtimes, downtime
default timeframe changed to 4 hours (see issue #35)
- vlog behavior altered to be more intelligent (for details see issue
#36))
- Implemented function for scheduling downtime for Nagios/Icinga
hostgroups (see issue #37) [parameters -g / --downtime-hostgroup,
satprep_prepare_maintenance.py]
- Some minor fixes

- added satprep_patch_freeze for automatic cloning of affected channels
and mapping subscribed hosts
- moved function is_blacklisted into satprep_shared.py
- enabled satprep for Spacewalk 2.4

Fixed typo

Fixed issue #7

Enhanced satprep_patch_freeze.py:
- enhanced error reporting to also include XMLRPC errors
- changed „-satprep“ prefix to „.sp“ to shorten names (several RHN
Satellite releases seem to have problems with that)
- removed some old rubbish

Fixed several bugs:
- custom info key values are now escaped to avoid aborts (added shared
function escape_string; see issue #49)
- when cloning channels, labels are added to the name (see issue #47)
- changed name format to „label-date.channel“ when cloning channels to
avoid using protected names (see issues #46 and #48)
- fixed a bug to avoid scheduling downtimes for non-monitored hosts
- fixed a bug where VM snapshots were not created
- fixed a bug where wrong reboot_required information were inserted
into patch reports
- fixed a bug where diff reports could not be created (see issue #44)
- verification log files are created if non-existent
- added support for Spacewalk 2.4

Fixed various bugs:
- fixed a bug where monitoring information were incorrect in the PDF
reports
- fixed a bug where debug information where printed in satprep_diff.py
without explicitely enabling it
- fixed a bug where child channels were not cloned correctly (see issue
#50)

Also, satprep_snapshot.py will now include patch information by default
(omitting the -p parameter, see issue #51). Using -p will now exclude
patch information!

Hosts without valid base-channel will now be ignored by
satprep_patch_freeze.py (Fixed issue #50)

Fixed a bug where the script crashed because of a missing local variable

Fixed a minor bug where prefix were based on ctime instead on mtime