Allow custom path for exports from Confluence

Client has requested that exports be enabled to locations other than Confluence-Home/temp directory in order to be able to utilise disk space on another partition/mount point. This would require that the disk partition and/or mount point has the proper permissions for the Confluence user (that Confluence runs under) , and this would be a user-configured option. Customer would like to keep the Confluence home space for other uses and send exports external to the Confluence-Home directory.