reworking for Import/Export UI (#4128)

this commit includes the GUI to manage import/export/reset of SNMP, AM, User Scripts and Notification

scripts/lua/modules/lua_utils.lua

@@ -283,7 +283,7 @@ end
 function sendHTTPContentTypeHeader(content_type, content_disposition, charset, extra_headers, status_code)
   local charset = charset or "utf-8"
   local mime = content_type.."; charset="..charset
-  
+
   sendHTTPHeader(mime, content_disposition, extra_headers, status_code)
 end
 
@@ -3910,6 +3910,12 @@ end
 
 -- ###########################################
 
+function table.has_key(table, key)
+   return table[key] ~= nil
+end
+
+-- ###########################################
+
 
 --
 -- IMPORTANT