sum = function(values, multiplier) { //make the sum of all array values
			multiplier = multiplier || 1;
			var res = values[0];
			for (var i = 1; i < values.length; i++) {
				res = res + (values[i]*multiplier);
			}
			return res;
		}
Canvas reset/resize methods: put back the canvas to its default values

depending on options, can set color, size, background back to default values
and store the reseted canvas in webstorage and history queue

resize values depend on the `enlargeYourContainer` option