get_query_payload should return the sql/tap query when available

[bsipocz]

I feel it would be more useful to have the sql/tap query returned with get_query_payload kwarg rather than the input dictionary when available. The logic with the kwarg is to provide a convenient way to debug problematic queries and it should return whatever is sent to the server.

E.g. instead of {'table': 'kelttimeseries', 'format': 'ipac'} I would like to get "select * from kelttimeseries where kelt_sourceid='KELT_N02_lc_012738_V01_east' kelt_field N02" that is more appropriate to plug into the web interface.

I've run into this with the nasa_exoplanet_archive module, but it's possible that other modules do the same, too.

[bsipocz]

All modules have been checked and fixed.