Debugger: Retry connection to host.

Connection to the server will fail immediately on non-Windows platforms. In these cases, the program will attempt to retry the connection on an interval up to a certain number of times before failing.

Added icons and custom boot splash.

Each platform has the appropriate icons file provided along with the Krita project file with the icon in vector graphics.
The splash screen is a 1024 image.

Update README description of snippet.