Add docs for hook_civicrm_alterLocationMergeData
Created by: JKingsnorth
There wasn't any documentation for hook_civicrm_alterLocationMergeData, so I thought we should create something! It was introduced in 4.7.10.
@eileenmcnaughton is there anything you think we should add to this?
It would be good to get something basic up, which we can embellish later if needed.
I'm not sure if I've edited this in all the right places, let me know if I need to make any changes.