r2.0.0-rc4

2.0.0 Release Candidate 4

Please see our pre-release announcement.

Changes since r2.0.0-rc3:

• Replace kvdb_profile utility with CLI command
• Improve QoS when using a staging media class
• Add a high-level KVDB format version to kvdb.meta file
• Minor API changes in converging to stable API
• Various bug fixes and performance enhancements