[FEATURE]: Union loggers should have ‘nowritefile’ input-switch like other monitors

[willend]

Is your feature request related to a problem? Please describe.
In the case of long and complex instruments, I often include monitors that are optional, i.e. that do not measure / do not save output depending on an instrument input var, i.e.

COMPONENT Mymon = Some_monitor(… , nowritefile=(!all_outputs))
WHEN all_outputs AT (0,0,0) RELATIVE somewhere

• which will only perform measurements / store output if all_output !=0

Describe the solution you'd like
Since all monitors/ and most monitors from contrib/have this possibility, It_ would be reasonable that the Union loggers had the same feature.

[mads-bertelsen]

Would be happy to add that if helpful, I don't foresee any issues in adding it exactly as on other monitors, as the SAVE block is used as normal on each logger regardless of their interaction with Union_master. Hope to have it ready within the week!