Collections Overview (preview) page

With the help of Perry Krug, we came up with a succint message for what are collections and how they are useful that is captured in the following blog. There is a neat diagram too which captures a canonical use case for Collections. It would be great to capture the content of this blog along with the diagram in our documentation.

Link to blog: https://blog.couchbase.com/introducing-collections-developer-preview-in-couchbase-server-6-5/