The recently introduced PACKAGE_FEED_PREFIX is not flexible enough for
constructing URIs, because the same PREFIX is used for all PACKAGE_FEED_URIS.
Also, the string 'PREFIX' is confusing because it is not at the beginning of
the URI. The variable PACKAGE_FEED_BASE_PATHS replaces PACKAGE_FEED_PREFIX,
allowing multiple base paths to be appended on each PACKAGE_FEED_URIS. In the
other hand, a new variable called PACKAGE_FEED_ARCHS, similar in concept to
PACKAGE_BASE_PATHS, defines package architectures defined by the user.
To demonstrate the usage of the PACKAGE_FEED_URIS, PACKAGE_FEED_BASE_PATHS and
PACKAGE_FEED_ARCHS, let's assume these variables are set on local.conf
