Fix a bug in ValidationCodeDialog

Add dispose after clicked confirm button
Add file path the the image
Use string map instead of NameValue list in NetOperationInterface
Modified WebClientInterface

Add generateFormParams method to convert a map to a name value pair
list.
Remove unneccessary doGet/doPost method.
Modified DefaultWebClient

Implement new methods;
Remove unneccessary methods.
Modified DefaultConnection

Change List<NameValuePair> formParams to Map<String, String> paramsMap
Modified DefaultCore

Implement new methods