Preventing fields=* calls

Adding in explicit code to prevent users from making calls and passing fields=* as the requested field set. This is still allowed for /meta calls (because the number of records returned is static), but for any calls pulling real data, passing fields=* into the SDK BullhornData object will result in a NoAllFieldsException being thrown.

You can always use a /meta API call to determine the full list of fields, and manually pass those into your BullhornData method call.