Issue LIBCLOUD-407: Better name for Node drivers

Some classes in libcloud.compute.drivers aren't easily identifiable in
the supported provider matrix due to their name attributes being
generic. This change adds detail to NodeDriver classes where there are
multiple per provider, e.g., Amazon EC2.

Signed-off-by: Tomaz Muraus <tomaz@apache.org>
Merge branch 'trunk' of https://github.com/apache/libcloud into trunk