Add an option group to the status key to allow separation of prefetch status from normal page status.

Closes #116 
Perhaps, but given the broad usage, I'd prefer to avoid the repeated array creation and iteration.  Also, the tighter type-annotation of the arguments version will allow better optimization and error checking.  (We should probably actually change the second arg to be {string} to allow possible string joining during compilation.)

No problems with renaming the function.