Isolation mode trigger

[Forboding Angel]

Need a way to trigger isolation mode, and set it to = Current Directory without using a system environment variable. This way, spring can be launched directly without having to be launched via a command line script or manually setting the env var first.

A simple file in the spring directory would do the trick nicely. SOmehting names like "isolated". When spring starts, if isolated file exists || if env var SPRING_ISOLATED is set, isolationmode = true, else, do the normal stuff.

It's a bit more involved than that because the env var can actually contain a path that spring will use for the datadir, but you understand the idea.