added feature to enable transparent sides, enhancement #3

	modified:   qgis2threejs.py
	modified:   qgis2threejsdialog.py
	modified:   qgis2threejsdialog.ui
	modified:   qgis2threejsmain.py
	modified:   template.html
	new file:   template_no_sides.html
	modified:   ui_qgis2threejsdialog.py