[REF] export code simplification

[REF] export code simplification

On review I find the value ['exportOption'] is a parameter used at the form later to determine whether to
export 'Primary fields only' (ahem) or the user should select an array of fields. By the time the form is submitted we
either have an array of selected fields or NULL denoting that there is no selection (& hence the defaults should be used)
and the selection at the form layer is redundant. However it is still being referenced in one place (and hence the tests
are passing it in to avoid an enotice). This fixes that one place & removes it from the tests. It also extracts part of
a test to move towards making it easier to alter the signature of exportComponents without messing with so many places in
the code