DOCS: IMDG Reference Manual: Minor improvement propositions for intro page

https://github.com/hazelcast/imdg-docs/blob/master/docs/modules/ROOT/pages/index.adoc
Current text:
**"This reference manual mostly talks about the Hazelcast member and clients in Java language. Although, the core of Hazelcast IMDG is based on the Java programming language, it has the following clients and programming language APIs."**
Propositions:
1. Hazelcast member and clients -> Hazelcast member**S** and clients
2. IMDG is based on the Java programming language -> I believe IMDG is using Java as a technology (it runs on JVM), thus, I think, more common term for that "IMDG is a Java-based solution"
3. This reference manual mostly talks about the Hazelcast member and clients in Java language - > For me, it sounds like Java clients and members are more important (preferable) than others. As far as I remember, more often it is constructed just like "Most of examples are written in Java".
4. Previous sentence -> If I'm not missing the whole picture, we don't have members on other languages, just clients, probably, it's better to change this part "mostly talks about the Hazelcast member ... in Java language"
5. programming language APIs - > For me, it sounds like an API to programming language. Probably, it could be changed to something like "clients and APIs in following programming languages"