updated todo...

Signed-off-by: Alex A. Naanou <alex.nanou@gmail.com>
started work on buildcache data update mechanics...

Signed-off-by: Alex A. Naanou <alex.nanou@gmail.com>
buildcache now adds new images correctly (still not done), marks.json and it's versions are now optional...

Signed-off-by: Alex A. Naanou <alex.nanou@gmail.com>