RFR 8150840: Add an internal system property to control the default level of System.Logger when java.logging is not present.

[Daniel Fuchs]

Hi,

Please find below a patch for:

https://bugs.openjdk.java.net/browse/JDK-8150840
8150840: Add an internal system property to control the default
          level of System.Logger when java.logging is not present.

This patch also introduces a better separation between the
SimpleConsoleLogger (created by the DefaultLoggerFinder
when java.logging is not there), and the SurrogateLogger,
which emulates the behavior of java.util.logging.Logger
when java.logging is present but there is no custom
configuration (used to be PlatformLogger.DefaultLoggerProxy).

best regards,

-- daniel