dog: add a new subcommand "dog vdi object dump-inode" for diagnosing inode object

How to use:
$ dog vdi object dump-inode <path of inode file>

Cc: MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>
Cc: Valerio Pachera <sirio81@gmail.com>
Cc: Alessandro Bolgia <alessandro@extensys.it>
Signed-off-by: Hitoshi Mitake <mitake.hitoshi@lab.ntt.co.jp>
sheep: reduce needless remove request during object reclamation

Cc: MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>
Cc: Valerio Pachera <sirio81@gmail.com>
Cc: Alessandro Bolgia <alessandro@extensys.it>
Signed-off-by: Hitoshi Mitake <mitake.hitoshi@lab.ntt.co.jp>
sheep: update store format version to v5

This patchset introduces two important change for sheep store:
1. generational reference counting: adding ledger object and expand
   inode object for generation reference
2. changing a place of btree_counter in inode object

Incrementing SD_FORMAT_VERSION in either of them would be
confusing. So this independent patch updates the number.

Cc: MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>
Cc: Valerio Pachera <sirio81@gmail.com>
Cc: Alessandro Bolgia <alessandro@extensys.it>
Signed-off-by: Hitoshi Mitake <mitake.hitoshi@lab.ntt.co.jp>
tests: show ledger objects in list

Cc: MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>
Cc: Valerio Pachera <sirio81@gmail.com>
Cc: Alessandro Bolgia <alessandro@extensys.it>
Signed-off-by: Hitoshi Mitake <mitake.hitoshi@lab.ntt.co.jp>
doc: add documentation of object reclaim algorithm

Cc: MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>
Cc: Valerio Pachera <sirio81@gmail.com>
Cc: Alessandro Bolgia <alessandro@extensys.it>
Signed-off-by: Hitoshi Mitake <mitake.hitoshi@lab.ntt.co.jp>
tests/functional: add test for object reclaim

This patch also removes existing test 086. 086 tests the clone
functionality and it depends on a max number of clones. But the object
reclaim scheme removes the maximum number. Hence the test becomes
obsolete. This patch adds a new test for the object reclaim as 086.

Cc: MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>
Cc: Valerio Pachera <sirio81@gmail.com>
Cc: Alessandro Bolgia <alessandro@extensys.it>
Signed-off-by: Hitoshi Mitake <mitake.hitoshi@lab.ntt.co.jp>
update CHANGELOG.md for new object reclaim scheme and "dog vdi object dump-inode"

Cc: MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>
Cc: Valerio Pachera <sirio81@gmail.com>
Cc: Alessandro Bolgia <alessandro@extensys.it>
Signed-off-by: Hitoshi Mitake <mitake.hitoshi@lab.ntt.co.jp>
tests/functional: add a new test of the object reclaim for cloned VDIs

This patch adds a new test of the object reclaim algorithm. The test
creates branch of VDI tree and checks the GC works well for the case.

Cc: MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>
Cc: Valerio Pachera <sirio81@gmail.com>
Cc: Alessandro Bolgia <alessandro@extensys.it>
Signed-off-by: Hitoshi Mitake <mitake.hitoshi@lab.ntt.co.jp>
tests/functional: new test of object reclaim for a case of continuously snapshotted VDI

Cc: MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>
Cc: Valerio Pachera <sirio81@gmail.com>
Cc: Alessandro Bolgia <alessandro@extensys.it>
Signed-off-by: Hitoshi Mitake <mitake.hitoshi@lab.ntt.co.jp>