Version checker

Occasionally a new version of SIP Inspector becomes available. The program checks for it when it starts. The check runs in the background, so the main window is shown at once and it never waits for the network. If a newer version exists a window offers to download it; sometimes a message from the author is shown. Licenses bought for version 7 allow downloading any update of 7.xx for free. Updates are usually bug fixes or smaller features that make the program faster, better and more functional.