【优化】通用HTTP任务（httpJobHandler）优化，任务参数格式调整为json格式；示例参数如下：

xxl-job-executor-samples/xxl-job-executor-sample-frameless/src/main/java/com/xxl/job/executor/sample/frameless/jobhandler/SampleXxlJob.java

@@ -174,12 +174,13 @@ public class SampleXxlJob {
             XxlJobHelper.handleFail();
             return;
         }
-        if (method==null || !Arrays.asList("GET", "POST").contains(method)) {
+        if (method==null || !Arrays.asList("GET", "POST").contains(method.toUpperCase())) {
             XxlJobHelper.log("method["+ method +"] invalid.");
 
             XxlJobHelper.handleFail();
             return;
         }
+        method = method.toUpperCase();
         boolean isPostMethod = method.equals("POST");
 
         // request

xxl-job-executor-samples/xxl-job-executor-sample-springboot/src/main/java/com/xxl/job/executor/service/jobhandler/SampleXxlJob.java

@@ -176,12 +176,13 @@ public class SampleXxlJob {
             XxlJobHelper.handleFail();
             return;
         }
-        if (method==null || !Arrays.asList("GET", "POST").contains(method)) {
+        if (method==null || !Arrays.asList("GET", "POST").contains(method.toUpperCase())) {
             XxlJobHelper.log("method["+ method +"] invalid.");
 
             XxlJobHelper.handleFail();
             return;
         }
+        method = method.toUpperCase();
         boolean isPostMethod = method.equals("POST");
 
         // request