Settings JSON configuration files can now specify default scalar bar
titles for arrays of specific names. In a settings JSON file, a
`<custom title> `for `<array name>` can be specified with the
following JSON structure:

{
  "array_lookup_tables" :
  {
    "<array name>" :
    {
      "Title" : "<custom title>"
    }
  }
}

Custom titles can only be read from JSON - this change does not
include a mechanism to save custom titles from ParaView.