Multiple Outputs Mark II

[jipperinbham]

_NOTE_
_BREAKING CHANGE_
Once this is merged, all existing config.toml files will be invalid and need to be updated. All examples in the project have been updated with the new format.

Attempt to move the InfluxDB client into an outputs pkg to allow for different outputs in the future.

@sparrc there's still some merge conflicts but I've done my best to get everything as close to master as possible where I can. Everything has been go veted and golinted.

[pauldix]

Output interface should have a Close() error method so Telegraf can be cleanly shut down. Maybe in a separate PR?

I'm cool with the breaking change. Sad we have to make it, but everyone will be better for it :)

[jipperinbham]

Good thought on adding Close() to the interface. As soon as #109 is merged, I can get that in shortly after.

I made a few attempts to not make it such a breaking change but couldn't ever settle on a config format that didn't seem like magic.

[sparrc]

Closing this PR because it got covered by PR #109, apologies that most of your commits got covered up, the rebasing got a little bit crazy ;-)

Thanks so much @jipperinbham! This is huge!

[jipperinbham]

@sparrc thanks for all the help getting this in! Hope to get started on a new output soon.