Allow configuration of solo.rb via knife.rb

The latest rendition of this uses .chef/knife.rb entirely and munges all paths into a generated solo.rb.

Changing the root "provisioning path" (name borrowed from vagrant) can be done via command line switch.

The rest is not customizable on the node and is considered an implementation detail. Instead this will read all of the local knife.rb configurations and use them as the source path during rsync.

This is working well in my testing so far, but the downside is that we now rsync everything separately which makes all this even slower given the ssh connection overhead.

I'm inclined to accept that for now since it's puts more pressure on the planned ssh-connection refactoring which should really happen anyway.

For testing the latest version, just remove solo.rb and re-run `knife solo init .` to generate `.chef/knife.rb`. Or if you have one already just make sure it includes the items listed in [the example](/matschaffer/knife-solo/blob/9e04f88152a2ef068e726ec51ec0e5d681e328a7/lib/knife-solo/resources/knife.rb).

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