修复曲线图表值为负数时Y轴上无法显示的BUG

ureport2-core/src/main/java/com/bstek/ureport/chart/Chart.java

@@ -83,7 +83,7 @@ public class Chart {
 		}else{
 			if(withoption && hasYAxes(dataset)){
 				sb.append(",");
-				sb.append("\"scales\":{\"yAxes\":[{\"ticks\":{\"min\":0}}]}");				
+				sb.append("\"scales\":{\"yAxes\":[]}");				
 			}
 		}
 		sb.append("}");

ureport2-core/src/main/java/com/bstek/ureport/chart/axes/impl/YAxes.java

@@ -30,7 +30,6 @@ public class YAxes extends BaseAxes {
 		StringBuilder sb=new StringBuilder();
 		sb.append("{");
 		sb.append("\"ticks\":{");
-		sb.append("\"min\":0,");
 		sb.append("\"minRotation\":"+getRotation()+"");
 		sb.append("}");
 		ScaleLabel scaleLabel=getScaleLabel();