ResourceEditor: Keep compress and threshold attributes

These aren't editable but at least keep them the same.

Change-Id: I75a907c9523766de2ee671f150b1180ab60cfae9
Reviewed-by: Jarek Kobus <jaroslaw.kobus@digia.com>
Reviewed-by: hjk <hjk121@nokiamail.com>
ResourceEditor: Remove dead code

Change-Id: I80456fb855d8af46bae79b77f60a61c31d76e219
Reviewed-by: hjk <hjk121@nokiamail.com>
Reviewed-by: Jarek Kobus <jaroslaw.kobus@digia.com>
ResourceEditor: A prefix is uniquely identified by prefix + language

So add checks for language everwhere.

Change-Id: Iba1035065f34d2008b53f1c73518eb5ad5c54850
Reviewed-by: hjk <hjk121@nokiamail.com>
Reviewed-by: Jarek Kobus <jaroslaw.kobus@digia.com>
ResourceModel::changeLang(): Prevent duplicated prefixes

Do the same check as changePrefix

Change-Id: I8edf6641295c9c38fbcc70fc5610dba275547b8a
Reviewed-by: Jarek Kobus <jaroslaw.kobus@digia.com>
Reviewed-by: hjk <hjk121@nokiamail.com>