archiver.bbclass: set deploy dir in a global variable

The archive deploy destination needs to be the same in every case that
it is used. Set the default path to '${DEPLOY_DIR}/sources' in global
variable 'ARCHIVE_DIR'. As a bonus, this allows the destination to be
redefined. Also, use os.path.join instead of regular string concatenation.

Signed-off-by: Kevin Strasser <kevin.strasser@linux.intel.com>
archiver.bbclass: make filtering more consistent

Consolidate the functionality from not_tarball and tar_filter
into a single function called archive_exclude. All archiving
methods test the current recipe against archive_exclude before
proceeding.

Signed-off-by: Kevin Strasser <kevin.strasser@linux.intel.com>
archiver.bbclass: move kernel archive statement

In the case where archiver.bbclass is being inherited to access
the copyleft filter functionality, it is unexpected for the kernel
to be archived. Move this statement out to the classes that need it.

Signed-off-by: Kevin Strasser <kevin.strasser@linux.intel.com>