Lots of UI changes/fixes for the new SDM dataset and layer selection interfaces.
Merge branch 'validation_changes' of git://github.com/BCCVL/org.bccvl.theme into validation_changes
Force validation to use error messages from element attributes if possible.
Merge branch 'validation_changes' of git://github.com/BCCVL/org.bccvl.theme into validation_changes

Conflicts:
	org/bccvl/theme/theme/html/js/bccvl-widgets.js
	org/bccvl/theme/widgets/dataset_input.pt
	org/bccvl/theme/widgets/datasetlayers_input.pt