Default preset

This implements #804, although I'm still not keen on the idea. I've attempted to make myself feel better about the whole nondeterministic-behaviour element of allowing users to change the behaviour of apps which are scripted as part of the pipeline by never autoloading the preset if either `-preset` or `-arguments` is specified on the command line - in that case I assume someone is scripting the app to launch it with specific settings for a reason…and that they wouldn't want those settings clobbered...