SleepAppender can derive from UnsynchronizedAppenderBase

Unsynchronized means no synchronization keyword in the doAppend method.

UnsynchronizedAppenderBase is based on Ralph Goers contribution in LBCORE-58. 
Note that AppenderBase remains unchanged. Appenders which need to handle synchronization on their
own can do so by deriving from UnsynchronizedAppenderBase.

- detachAppender in AppenderAttachable now returns a boolean instead of an Appender.
- iteratorForAppenders() in AppenderAttachable now returns Iterator<Appender<E>> instead of just Iterator
- modified Logger to invoke callAppender without synchronization on this
- AppenderAttachableImpl modified to take advantage of the fact that reads occur much more 
  often than writes
- associated test cases

This change is related to LBCORE-52.

Test that Joran does continues processing in presence of errors and that 
it registers status messages

In WriterAppender, getPresentationFooter and getFileFooter are now printed in the correct order, 
presentation footer first, file footer last.

Improvements to the section regarding parentheses in PatternLayout

the bestEffortLoadClass returns null.

the callerClass computed by R.getCaller class can be null.

Added documentation and test cases for STARTTLS and SSL support.

Added support for plain user password authentication. 

Furthermore, support for both STARTTLS and SSL connections were
added. Note that STARTTLS differs from SSL in that, in STARTTLS, the
connection is non-encrypted in the beginning and only after the STARTTLS 
command is issued by the client (if the server supports it) does the 
connection switch to SSL. In SSL mode, the connection is SSL from the 
start.

FileAppender will now automatically create parent directories as needed.

- added unit tests 
- updated the documentation

- Allow TimeBasedRollingPolicy to delete old files if asked by the user.
- PeriodicityType are now listed in an enum.

- renamed ClassPackagingDataCalculator as PackagingDataCalculator
- added calculatePackagingData method to ThrowableProxy so that converters can
  force calculation of packaging data
- added relevant test cases

Increase slack factor to 8 for Sun's JDK 1.6. For some reason, slack factor of 6 for JDK 1.5 was insufficient.