setup-mel-builddir: auto pull in update-* layers

JIRA: SB-2051

Signed-off-by: Christopher Larson <kergoth@gmail.com>
mel: warn if there are update layers not included

JIRA: SB-2031

Signed-off-by: Christopher Larson <kergoth@gmail.com>
archive-release: archive update-* layers individually

JIRA: SB-2030

Signed-off-by: Christopher Larson <kergoth@gmail.com>
Merge pull request #104 from kergoth/updates

Necessary pieces for our release updates handling