Add ability to stop Test connection

​@Stefán Gunnar Jóhannsson I believe the only way is to force quit the application

​@Stefán Gunnar Jóhannsson are you able to reproduce the hang? how long does it hang for? If so can you please send the data source settings in a support ticket to support@timextender.com . Also please include any error messages from the event viewer

I have converted this to a product idea