#8 Change destructive displaying in Logger

[Alexander Verbraeck]

Currently, the default behavior of the LogPanel and
LoggerFrame Logger is that when messages for a certain
package have been displayed, and the window has been
closed, the messages can not be shown again. This is
inconvenient for users who want to get back to a set of
logmessages after a while, or who want to compare
messages for different packages, and closed one of the
windows by accident or because they thought they
would not need the information anymore. As the buffers
have limited size anyhow, why not keep the information
for redisplay - or for remote display to more than one
user, which is now also impossible.