[#6591] - Bug in copy constructor of ClientInputControl class from jasperserver-dto module

Copy constructor of ClientInputControl class does not call base class copy constructor. Discovered during work on rest client utilising jrs-rest-java-client library. Due to this bug it is not possible to create new Input Control resource from copy of ClientInputControl object returned by its copy constructor - always returns "Bad request" error. Also I would suggest to check if original object has visibleColumns list and if it is null, do not copy it, since not each type of Input Control needs to have it. I have attached modified file which fixed these issues for me.