conf/bitbake.conf: default HOMEPAGE to blank instead of unknown
The default value for HOMEPAGE of "unknown" has been in place since the
early OE-Classic days, but it doesn't really make sense - "unknown" is
not a valid URL and it just means we have to explicitly check for this
hardcoded string if we're displaying the value in some form of UI, such
as Toaster.
This has required some changes to the packaging classes as they
previously did not expect the value to be blank.
Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com> Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
