Test Pull: 1 file to change: add field parent_id in tasks

update 2012-12-10: committed all sub-task implementation so far - more to come later.
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field parent_id for sub-task feature
want to test the pull, so only one mini-change in the setup/upgrade/1.0.0/flyspray-install.xml
i'm going to commit my other changes to my fork now, and send another pull request later, when this one has been pulled
hope, it works
enjoy! :-)