Add option to override expire clients for tile layer
Handmade merge with http://jira.codehaus.org/browse/GEOS-6020
Merge branch 'master' into expireClients
Merge branch 'master' of https://github.com/geoserver/geoserver into expireClients
Forgot to unset transient members from patch
Merge pull request #315 from sweco-sebhar/expireClients

Add option to override expire clients for tile layer