improve efficiency of multilayered indirect blocks

clean up tests

panic cleanup

clean up logic, improve readability

add final root node to the dagservice upon creation

importer: simplified dag generation

test: updated hashes using latest code

@whyrusleeping this is why the sharness tests
were failing: the hashes are added manually to
make sure our generation doesn't change.

cleanup after CR

fix merkledag tests

fix small block generation (no subblocks!)