feature：增加obs归集方式 (#90)

* feature：实现通过datax进行obs归集的插件

* feature：前端增加obs归集时的前缀参数

runtime/datax/obsreader/src/main/resources/plugin.json

@@ -0,0 +1,6 @@
+{
+  "name": "obsreader",
+  "class": "com.datamate.plugin.reader.obsreader.ObsReader",
+  "description": "read from obs file system",
+  "developer": "datamate"
+}

runtime/datax/obsreader/src/main/resources/plugin_job_template.json

@@ -0,0 +1,10 @@
+{
+  "name": "obsreader",
+  "parameter": {
+    "endpoint": "127.0.0.1",
+    "bucket": "test",
+    "accessKey": "ak-xxx",
+    "secretKey": "sk-xxx",
+    "prefix": "/test"
+  }
+}