Adding MASK filter strategy

[jzonthemtn]

With this filter, you can replace text with a given character of some arbitrary length or the same length. An example filter profile is:

{
   "name": "email-address",
   "identifiers": {
      "emailAddress": {
         "emailAddressFilterStrategies": [
            {
               "strategy": "MASK",
               "maskCharacter": "*",
               "maskLength": "same"
            }
         ]
      }
   }
}