Adding Progress Indicator

[john0005]

These samples should add a Progress Indicator. Sometimes when I run them I think they are broke because it takes a little bit to load.

• WMS Layer
• Raster Function
• Raster Layer

[tschie]

I added one for WMS. The raster samples load fairly quickly for me. Also, their delay isn't caused by loading, instead it's the raster rendering which is a little more difficult to attach a progress indicator to.