Add a MatrixOptionList object

We can grab a matrix option type id with:

  item = InventoryItem.get(1)
  item.matrix_options_list.options.first.type_id

An instance would look like this:

  => #<NetSuite::Records::MatrixOptionList:0x007ffd54ae90d0
   @options=
    [#<OpenStruct type_id="529", value_id="9">,
     #<OpenStruct type_id="530", value_id="1">]>
Add custom_fields_by_type to Records::CustomFieldList

Help us get speficif types of fields without too much method chaining