Add new status of 'locked'.

Allows a field to be uneditable but shown straight away. No need to uncollapse the field to see the value.

I'm making a PR of this as the functionality is being requested on the forums. However, the way I've implemented it here is a bit of kludge as it breaks the semantics of the "collapsed" variable. Perhaps a simple change of the new value from 'locked' to 'collapsedNoButLocked' would be sufficient to restore your semantics. In addition, I pulled the fixed value of 16 out of thin air as I have no idea how you picked the original const values.