Removing sub-parts from the remote parts ecosystem.

[Joe Talbott]

Dear Snapcrafters,

The wiki introduced the concept of sub-parts and used namespacing to
associate a list of sub-parts with a project-part.  However the
concept was ill-conceived and now needs to be removed.  In essence,
all parts should be top level parts.  Each entry in the wiki should
identify one or more parts from a snapcraft.yaml file that are
considered to be useful to other snapcraft users.  A current example
of subparts might look like this:

   ---
   origin: https://github.com/josepht/snaptastic
   maintainer: Joe Talbott <joe.talbott at canonical.com>
   description: Some fun parts
   project-parts: fun-part
   parts: [a, b, c]

Which would produce parts ‘fun-part/a’, ‘fun-part/b’, and
‘fun-part/c’.  The new approach should be:

   ---
   origin: https://github.com/josepht/snaptastic
   maintainer: Joe Talbott <joe.talbott at canonical.com>
   description: Some fun parts
   parts: [fun-part, fun-part-a, fun-part-b, fun-part-c]

Where the hierarchy is removed and each part is a top-level part.  The
part names will need to be changed in the snapcraft.yaml file as well.


Thanks,
Joe