Change `CompleteAppTask` type to include task type

[bardram]

Change the completed app task type to also contain the task type, like this:

dk.cachet.carp.completedapptask.survey

For backward compatibility, we should probably keep the old type and upload both types of data.

This change should also be reflected in the protocol, which then would need ALL the different types.

But - wait until @yuanchen233 says "Go".