Changed to/from XML method sig.
Added method stubs for toXML() & fromXML() in abstract LogEvent class.
Added initial to/from XML to LogEntry.
 Fixed toXML() in KeyEvent class.
Added initial xml write functionality for data logger entries.
Updated LogEvent.toXML() implementation.
Added initial MouseEvent.toXML() implementation.
Added precondition to KeyEvent.toXML().
Fixed CompositeDataLogger.writeXmlLogEntry().
Updated TODO list and CHANGES.pod.
Partially implemented fromXML() methods in ConpositeDataLogger and LogEntry.
Implemented KeyEvent.fromXML().
Removed debugging code from KeyEvent.fromXML().
Fixed LogEntry.toString() for all implementations.
Changed LoggerPanel to format log entries better.
Fixed error handling of missing <event> tag in LogEntry.fromXML().
Implemented MouseEvent.fromXML() method.
Removed debug statement from MouseEvent.fromXML().
Fixed bug in MouseEvent.fromXML().
Implemented MouseClickedEvent.fromXML().
Implemented MouseDraggedEvent.fromXML().
Updated CHANGES.pod.
Implemented MousePressedEvent.fromXML() and MouseReleasedEvent.fromXML().