lib/oe/package_manager: Introducing PACKAGE_FEED_BASE_PATHS/PACKAGE_FEED_ARCHS

lib/oe/package_manager: Introducing PACKAGE_FEED_BASE_PATHS/PACKAGE_FEED_ARCHS

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

    PACKAGE_FEED_URIS = "https://example.com/packagerepos/release \
                         https://example.com/packagerepos/updates"
    PACKAGE_FEED_BASE_PATHS = "rpm rpm-dev"
    PACKAGE_FEED_ARCHS = "all core2-64"

the resulting feeds would be

    https://example.com/packagerepos/release/rpm/all
    https://example.com/packagerepos/release/rpm/core2-64
    https://example.com/packagerepos/release/rpm-dev/all
    https://example.com/packagerepos/release/rpm-dev/core2-64
    https://example.com/packagerepos/updates/rpm/all
    https://example.com/packagerepos/updates/rpm/core2-64
    https://example.com/packagerepos/updates/rpm-dev/all
    https://example.com/packagerepos/updates/rpm-dev/core2-64

(From OE-Core rev: 229723a20095e80bde29e4b3398047f62f972170)

Signed-off-by: Leonardo Sandoval <leonardo.sandoval.gonzalez@linux.intel.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>