Switched to use tsv instead of votable format for cone_search. Also corrected us of logging to logger and modified exist to only catch IOError class, other exception to not get cought.
added some debuging code to keep track of how frequently an image is loaded.  Looking for a memory leak.  Also, modified '_image_data'  property to be a but more direct.
code clean-up to ensure reference exist and code is closer to PEP-8
Moved mpc.TIME to its own module to remove circular reference.