Scripting: backport changes from es 1.6

From elastic/elasticsearch#10419

We need to adapt river code from es-1.x (1.6.0)

Closes #98.

src/main/java/org/elasticsearch/river/couchdb/CouchdbRiver.java

@@ -144,7 +144,7 @@ public CouchdbRiver(RiverName riverName, RiverSettings settings, @RiverIndexName
                 }
 
                 script = scriptService.executable(scriptType, couchSettings.get("script").toString(),
-                        ScriptService.ScriptType.INLINE, ScriptContext.UPDATE, Maps.<String, Object>newHashMap());
+                        ScriptService.ScriptType.INLINE, ScriptContext.Standard.UPDATE, Maps.<String, Object>newHashMap());
             } else {
                 script = null;
             }