Fix bug in getCopiedTasks of Data

see issue #160
Merge branch 'master' of
https://github.com/cs2103aug2014-f11-1j/TaskCommander.git
Update update methods to set the edited attribute to true

as discussed in WhatsApp
Merge branch 'master' of
https://github.com/cs2103aug2014-f11-1j/TaskCommander.git