Pls fix README, About section and Github issues template (remove rocksdb and add rocksdb-cloud support info)

[ramvadiv]

Note: Please use Issues only for bug reports. For questions, discussions, feature requests, etc. post to dev group: https://groups.google.com/forum/#!forum/rocksdb or https://www.facebook.com/groups/rocksdb.dev

Can you pls provide contacts for seeking support for rocksdb-cloud and avoid references to rocksdb. People seeking support for rocksdb-cloud seems to ask questions in rocksdb forums due to this.

Pls remove rocksdb contact info and add rocksdb-cloud contact info in the README.md, About section in the main page (that has reference to rocksdb.org) and the default note when Github Issues are created.