DOCS: IMDG Reference Manual: “Overview: Use Cases” - minor improvements

https://github.com/hazelcast/imdg-docs/blob/master/docs/modules/overview/pages/use-cases.adoc

1. Hazelcast can be used -> I would propose “HZ is best for” for better HZ promotion
2. with event notifications, e.g., user based events -> As for me, changing data already implies events which are changing it. Not-clear what is user-based events. Could it be specified?
3. and to queue and distribute background tasks -> I can’t imaging how background tasks are related to IMDG, probably, we could use here more obvious example?
4. as a cloud-wide scheduler of certain processes that need to be performed on some members -> I don’t think I could imagine how IMDG will schedule cloud processes, probably, it is a god idea to bring some clear example here? Also ‘member’ team is used for HZ member, not clear why it is used here
5. with multiple members -> It seems, instances of some service are mentioned here, but HZ member is a specific term, probably, we don’t need it here
6. to share keys in a cluster where there is a web service interface on an application server and some validation -> Not clear why keys are not part of previous (to share info), not clear what is “some validation”. Could we adopt it?
7. as a distributed topic (publish/subscribe server) to build scalable chat servers for smartphones -> I’m curious why “smartphones” are here? Do we have any mobile specifics? Could it be described a bit more?
8. as a front layer for a Cassandra back-end - > Could it be specified a bit? Why Cassandra need this front layer?
9. To distribute user object states across the cluster, to pass messages between objects and to share system data structures (static initialization state, mirrored objects, object identity generators) -> this is clashes with “to share information”, probably, they could be combined
10. to share datasets, e.g., table-like data structure, to be used by applications - > it seems, all data objects sharing could be combined in single unit for simplicity
11. to distribute the load and collect status from Amazon EC2 servers where the front-end is developed using, for example, Spring framework - > It seems a bit confusing to me - how we could distribute the load of EC2 instances? Probably, some additional details have to be highlighted
12. as a real-time streamer for performance detection -> Not clear for me what it performance detection in terms of IMDG, could we use some more particular example?
13. as storage for session data in web applications (enables horizontal scalability of the web application). -> not clear to me why we are describing data storage possibility one more time and why web applications are showed as separate example, do we have a really important use case here? Could it be described a bit?
14. I would proposer to add links to our code samples here (https://github.com/hazelcast/hazelcast-code-samples) As I see it, It is a really good idea group examples per particular use cases to have clear picture of “examples of best use cases”