Adding ability to compress log files as with gzip or zip. Added the definition and extended all places where log files are created.

A new option is now possible for the log files configuration, "compression" default is "", valid values are "gz", "zip", other values are considered ""
gz: compress the old log files (when rotated) with gzip
zip: compress the old log files (when rotated)with zip
Rotated log files can now end with "yyyy-mm-dd_hh-mm" or the same followed by ".gz" or ".zip"

creation/lib/cgWParams.py, creation/lib/cvWParams.py - parameter definition and default
doc/factory/configuration.html, doc/frontend/configuration.html - documentation
lib/logSupport.py - actual definition and actions
unittests/test_configurations/test_logSupport.yaml, unittests/test_logSupport.py, unittests/worker_scripts/log_writer.py - unit tests
creation/reconfig_glidein, factory/glideFactory.py, factory/glideFactoryEntry.py, factory/glideFactoryEntryGroup.py, frontend/glideinFrontend.py,
 frontend/glideinFrontendElement.py - uses (log files are defined using the factory/vofrontend configuration)
added note to wardn that max_bytes is truncated
wrapped compression operations in a try/catch and logging on stderr
Merge branch 'v3/6983' into branch_v3_2
Compression of log files, error to stderr if something goes wrong