Event registration log messages

When a command processor registers or unregisters with the server part of a pdserver for GUI events, an entry can be made in each of the servers' error logs. The server being asked to send GUI events to a command processor's entry looks like:

5010-426 Server pdserver2 received a register signal from communication 
daemon pdserver1.

The command processsor's entry looks like:

5010-454 Successfully registered to receive notification events from 
server pdserver2.

Whether the messages appear in the server's error log depends on the log severity level setting.