Add EntityStream support for POJO (non-Spring entities)

[tahan42]

Hi,

In entity stream queries and in repository methods, the index name is inferred from the model class name (the class annotated with @Document or @Hash).
With the new indexing options introduced in 0.9.2, we have now the possibility to manage indexes outside the redis om application.

So it would be helpful, to be able to specify an index name when doing a query or to define a custom index name for a model class (that would be used in the queries for that model).

WDYT ?

[bsbodden]

@tahan42 renamed the issue to cover only EntityStreams first, can you create another ticket for Repositories?