Add additional segment information to query results

[kbg]

The Client.query() method currently only returns segment locations. It would be useful in some cases to also have access to additional by-record segment information (like image dimensions) using the public drms interface.

At the moment this feature is only available using the internal HttpJsonClient instance, e.g.:

>>> import drms
>>> c = drms.Client()
>>> res = c._json.rs_list('hmi.sharp_cea_720s[][2012.03.06_TAI]', seg='magnetogram')
>>> res['segments'][0]['dims']
['705x387', '1006x434', '304x231', '163x105', '429x248', '553x375', '1167x460',
 '500x240', '248x117', '760x413']