(bf) Eliminate dependency on javax.management.ObjectName

The new management interface java.nio.BufferPoolMXBean results in an dependency on javax.management.ObjectName. This bug tracks eliminating the resulting dependency from the implementation. For example, java.nio.Bits and sun.nio.ch.FileChannelImpl can expose the details of the buffer pools and java.management.PlatformComponent can construct the BufferPoolMXBean. When the JDK is modularized then this would allow BufferPoolMXBean to be put into a management/jmx without a circularly dependency on a core or other module containing Buffers and FileChannel.