feature: bizcloud support

- templatized client.rb.erb
- removed ec2 hints from bootstrap script
- configurable http/https proxy for Chef
- no longer pulling down gpg key for chef opscode apt repo. doesn't
  seem to be needed and breaks the bootstrap
- pulling gpg key directly from opscode

Change-Id: I128e975a42aa2e7dc5fb84239b76881dd70ba4cc