Create region files for use with DS9

[MatthewWhiting]

A useful FITS viewer is SAOImage DS9, and it can accept region descriptions. The format is similar to Karma annotation files, but not exactly the same.

It would be good to provide the facility to write such a file, in the same manner as Karma annotation files.

[MatthewWhiting]

When doing so, perhaps incorporate the other output code into classes: make a base class for generic output, and have derived classes for each of the output types: results, karma, VOTable, DS9,...

[MatthewWhiting]

Region description for DS9 can be found at ​http://hea-www.harvard.edu/RD/ds9/ref/region.html

[MatthewWhiting]

Move this to 1.2.1 milestone, and compare with #158.

Whether the annotation file formats would come under the same generic TableWriter? class, or something else, is not clear at this point.

[MatthewWhiting]

With the new catalogue writer classes, it should be straightforward to derive a base AnnotationWriter? class, that defines functions for writing lines, circles, ellipses, etc. Then derive from that KarmaAnnotationWriter? and DS9AnnotationWriter classes, that do different implementations of these functions.

[MatthewWhiting]

Initial stage of this implemented in [1072], with a number of classes written as described above. Now to actually implement.

[MatthewWhiting]

This has been done. There are now input parameters flagDS9 and ds9File that work in the same way as the Karma ones. Have tested with ds9, and it works OK. The latest version of casaviwer appears to have gotten rid of the region interface, for some reason. (Maybe you can get to it via casapy?)

Anyway, this ticket is done, so closing.