SERVER-15296 RocksHarnessHelper for RocksSortedDataImpl

    Hook up RocksSortedDataImpl to sorted data interface tester
    Bunch of fixes in RocksSortedDataImpl. I'm not sure of some of the semantics since there is no interface documentation, but this seems to pass the unit tests
    Fix some compile issues due to upstream changes
    Fix RocksRecoveryUnit according to documentation in RecoveryUnit
    Fix rocks_sorted_data_impl_test

Closes #776

Signed-off-by: Benety Goh <benety@mongodb.com>