add new AddLibraryNameSuffix API for annotating connections with usage

[mgravell]

This usage is intended to help people identify their connections by usage; for example, by using:

conn.AddLibraryNameSuffix("cache");

the connection will be advertised as (by default) SE.Redis-cache. In particular, this targets scenarios where the ConfigurationOptions may be shared between uses, or otherwise unavailable, so it is not possible to simply add this to ConfigurationOptions