leveldb: Add paranoic checks and Restore database

:Release Notes:
Added paranoic checks for database corruption
If database is corrupted, try to restore it

:Detailed Notes:

:Testing Performed:
Compiled and tested locally

:QA Notes:

:Issues Addressed:
[GF-43278] DB8: Develop DB files integrity mechanism (e.g CRC32 based)

Open-webOS-DCO-1.0-Signed-off-by: Maksym Sditanov <maxim.sditanov@lge.com>

Change-Id: If644e1a41419282d516ccdf4b30ef0130d16e1cb
Reviewed-on: https://g2g.palm.com/3894
Reviewed-by: DCO Verification
Reviewed-by: Maksym Sditanov <maxim.sditanov@lge.com>
Tested-by: Maksym Sditanov <maxim.sditanov@lge.com>