CBD-1200: Add script to construct manifest from last-known-good build plus one change

Change-Id: I41ae6eb6824e1b6ee0985008fd8015de2030290e
Probably-incorrect attempt to bootstrap last-build-attempted manifest

Change-Id: I41ae6eb6824e1b6ee0985008fd8015de2030290e
More sensible initialization of last-build-attempted from last-known-good manifest

Change-Id: I41ae6eb6824e1b6ee0985008fd8015de2030290e