[FEATURE] PNG added to the url format

The old URL format http://server/plantuml/img/... is now relaced by
http://server/plantuml/png/...

src/main/java/net/sourceforge/plantuml/servlet/ImgServlet.java

@@ -34,7 +34,7 @@ public class ImgServlet extends UmlDiagramService {
 
     @Override
     public String getSource(String uri) {
-        String[] result = uri.split("/img/", 2);
+        String[] result = uri.split("/img/|/png/", 2);
         if (result.length != 2) {
             return "";
         } else {

src/main/webapp/WEB-INF/web.xml

@@ -52,6 +52,10 @@
 		<servlet-name>plantumlservlet</servlet-name>
 		<url-pattern>/form</url-pattern>
 	</servlet-mapping>
+    <servlet-mapping>
+        <servlet-name>imgservlet</servlet-name>
+        <url-pattern>/png/*</url-pattern>
+    </servlet-mapping>
 	<servlet-mapping>
 		<servlet-name>imgservlet</servlet-name>
 		<url-pattern>/img/*</url-pattern>

src/main/webapp/index.jsp

@@ -7,7 +7,7 @@
     <c:set var="hostpath" value="http://${pageContext.request.serverName}${contextroot}" />
 </c:if>
 <c:if test="${!empty encoded}">
-    <c:set var="imgurl" value="${hostpath}/img/${encoded}" />
+    <c:set var="imgurl" value="${hostpath}/png/${encoded}" />
     <c:set var="svgurl" value="${hostpath}/svg/${encoded}" />
     <c:set var="txturl" value="${hostpath}/txt/${encoded}" />
     <c:if test="${!empty mapneeded}">