[bin] Minor fix in comments.

[ci skip]
Fix a few exception messages.
Rename examples and update some comments.

[ci skip]
Fix a few exceptions.
Apply fixes for consistency.

I know that importing classes and interfaces for the root namespace
using the "use" directive is weird and totally uncommon...
Improve handling of -MOVED and -ASK responses.

This change improves code reusing and simplifies the internals of
our redis-cluster connection backend.
Do not throw exception when connection has been already established.

The base abstract connection class now returns a bool to indicate when
the actual connect() operation has been performed on the underlying
resource. This return value is not part of the interface so extending
classes can decide to not return any value.