Repair updated for edge case created with new directory structure.
intentionally ignore potential problems in highest level.  need much more complex code to address correctly.
not reusing block_cache during second phase of repair.  looks ok today, but there could be edge cases not seen or future code that would break assumptions.
Merge branch 'mv-repair-by-level' of github.com:basho/leveldb into mv-repair-by-level
Merge pull request #78 from basho/mv-repair-by-level

Repair updated for edge case created with new directory structure.