Move tags to support multiple layers in widget configuration.

Move tags (defaulttransparency, classificationFromColorRamp, classificationToColorRamp) to children of layer.
Add variables for layer configuration and scale dependent labels display warning.
Add fault handler for thematic layer, remove generic fault handler, add fault handlers for details and generate renderer tasks.
Update configuration load parsing to handle multiple layer configurations.
Add configuration initialization to widgetConfigLoadedHandler and add drop down list to support multiple layers.
Add function to setup and initialize active thematic layer.
Add one-time alert message when dynamic labels are turned on, but not yet in visible scale range.
Formatting and comments.
Remove event listeners from thematic layer in load handler.
Add generate renderer task fault handler.
Add change handler for drop down list when changing active thematic layer.
Remove block groups from configuration file.
Merge branch '#18/add-support-multiple-thematic-layers' into develop