REFRESH(boolean) option on persist

Today a persist will rebuild if

1. The underlying file does not exist
2. The data has changed
3. The code has changed

For attribute manager (and elsewhere) we sometimes want rather more control over the rebuilding of the persist file. This CAN be kinda hacked via workflow and 'hand managing persist equivalents' using output - but this is painful and often leads to overbuilding.

What would be really useful was a

REFRESH(boolean)

option on the persist. When the boolean was true it would be a no-op (everything works as it does today). When set to FALSE then the persist would rebuild ONLY IF the underlying file did not exist. Otherwise it would use the data there.

NOTE: I don't need this super-urgently (Q2 2016 is around target); but I have a design that needs it. So if we cannot do this I need to know soon so that I can schedule in hacking around this ....