Dropbox config sync plugin

[csmith]

We should write a plugin that uses the Dropbox core API to sync DMDirc's config.

https://www.dropbox.com/developers/core/start/java

[greboid]

Whilst this is definitely a different issue, it would be nice to have a computer identity so you could set computer specific things, if we're going to go the syncing route this is probably something that would be helpful, maybe.

[csmith]

Yeah, figuring out what to sync and what not to is a bit hard.

Probably for the first go we'll just do everything (including actions, plugins, etc).

Then maybe either allow users to exclude certain things, or default to having some things as local-only.