Support basic VO conesearch capabilities.
The basic idea is to isolate the user from the details of which URLs should be used for any particular catalog. Indeed, the general approach is to support a variety of servers and try each in order until one is found that is responsive. For this reason, only the basic conesearch parameter are supported for the generic catalog name. The details of which servers to try is held in a local configuration file. This file is updated periodically from an STScI server (or mirror) to keep it current.
Do a conesearch on the selected catalog.
By default, it returns a record array. This intial version writes a temporary file. When completed it deletes the file. For reliabilty, a small query is tried to see if the server is responsive.
Determine if conesearch query resulted in a VOTable reporting errors
Returns True if errors were found. Not yet implemented