Allow changes to entries in locked periods with a password override per transaction instead of having to unlock the period through settings

There are sometimes legitimate reasons why something needs to be changed on a transaction in a locked period. 

It's all well and good going in and changing the locked period date to an earlier date to allow this, but I've lost count of the number of times I forget to go back and change it back to the correct date after making the change.

If we could just type in a password to override the warning for the specific transaction, it would be soooo much more secure, and noone else could accidentally slip a new transaction through while the period is unlocked.

This would need to have a separate permission in user role setups - unlike the generic access to "preferences" as a whole so we can REALLY keep this permission locked down to the bare minimum number of users.