[Thuban-list] added classification support

[Jonathan Coles]

The following initial updates are now in the cvs repository:


layer.py -- classification initialization calls

classification.py -- created class to encapsulate a layer 
                     classification. Supports specific data 
                     points and ranges.

load.py -- add support for loading classification information

save.py -- add support for saving classification information

classifier.py -- initial class for a dialog

mainwindow.py -- support for opening the classifier dialog

renderer.py -- support for drawing a layer with the classification
               information

iceland_sample_class.thuban -- iceland_sample with classification data

test_classification -- tests for the Classification class


--jonathan