Expose the build pack key
Keep track of the filename so the admin knows what was uploaded
Break out upload_bits
Remove exported key
Merge branch 'filename' of https://github.com/fraenkel/cloud_controller_ng into fraenkel-filename

Changes from https://github.com/cloudfoundry/cloud_controller_ng/pull/147.

Resolved merge conflicts with https://github.com/cloudfoundry/cloud_controller_ng/pull/149.

Signed-off-by: Matthew Boedicker <mboedicker@pivotallabs.com>

Conflicts:
	app/controllers/runtime/buildpack_bits_controller.rb
	app/models/runtime/buildpack.rb
	spec/api/api_version_spec.rb
	spec/api/buildpacks_api_spec.rb
	spec/controllers/runtime/buildpack_bits_controller_spec.rb
	spec/controllers/runtime/buildpacks_controller_spec.rb