Platform-specific settings

[rickrankin]

It would be nice to have a mechanism for specifying platform-specific settings. I'm currently using DKit on Windows, Mac and Linux, and I keep my ST3 settings synced between systems using the Dropbox mechanism suggested here. The problem is that when the settings sync, settings for the other two platforms are overwritten by the settings for the last platform I used. I've gotten around the problem so far by changing the default settings on each system rather than the user settings, but that seems a bit hack-ish.