Remove cfgtool, it's not useful anymore

Remove cfgtool, it's not useful anymore

cfgtool was used to dump the current config defaults into ./system_config
on the system it runs. It was manually invoked (usually on Linux) and
hence produced incorrect settings for Windows and OSX variants.

Since ea4bbcf5 Ardour binaries bundle a minimal empty system_config,
and the built-in defaults are used (correct for every platform).