bitbake: bitbake-layers: show-cross-depends: add option to ignore a layer

bitbake: bitbake-layers: show-cross-depends: add option to ignore a layer

By default, show-cross-depends shows dependencies on OE-Core (i.e.
"meta") which is not particularly useful. Add an option to allow you to
hide those. For example, to hide all dependencies on OE-Core:

  bitbake-layers show-cross-depends -i meta

Multiple layers can be specified by using commas as separators (no
spaces).

(Bitbake rev: 0e9062e65acbb05c1d9b3a9145eb866c3d562309)

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>