Remove providers directory

Modular code is gem based and we have been using fog-brightbox as a
prototype for a while now as a proof of concept.

Management of numerous gems within the code base did not look like it
could scale particularly well for fog.
Remove edge check for fog-brightbox

Pulling too many remote sources from all the providers will make this
check very unstable. We should assume that we are only dealing with
released gems.
Merge pull request #3058 from fog/remove_providers_directory

Remove providers directory