Add CDS Photometry Viewer

[jbudynk]

Add a component for the CDS Photometry Viewer search tool. This is an interface to the VizieR archives. Using a search radius and target name/position, cross-match photometry tables from the VizieR catalogs and add them to Iris.

Also provide a customized SAMP handler to intercept messages from the Photometry Viewer; a client using the CDS Photometry Viewer from a web browser may broadcast data to other SAMP-enabled applications.

For more information on the CDS prototype, see the Iris UDF.

[jbudynk]

A basic VizieR component has been added in Iris 3.0b1.

However, we do not have a SAMP handler for this. I will close this issue and create a new one for the CDS SAMP handler. Note that #33 mentioned the CDS SAMP handler, so I might piggy-back this issue to that ticket.