NRediSearch; prepare for deploy

add GetCachedDatabaseInstance - no need to "new" in GetDatabase for high-volume scenarios, for example GetDatabase() defaulting to DB zero

Add IncludePerformanceCountersInExceptions (defaults to false) to fix #587 (also fix broken nunit reference in one of the tests)

Add SslProtocols property to ConfigurationOptions

supporting status for being able to retry, if command was never sent over the wire.

If an UnauthorizedAccessException occurs and _disabled is set to true, ensure subsequent calls to this method will not cause another UnauthorizedAccessException. (#589)