On application which do not put data in the MDC, the CopyOnInheriteThreadLocal would
throw a NullPointerException.

Given dependencies on test-jar logback could not be build as 'mvn package' from 
a pristine local repository. One had to 'mvn install' first. 

- Added blurb on LBCORE-32 
- various updates to news.html

- In DynamicThresholdFilter, renamed the OnMatch as OnHigherOrEquals, 
  and OnMismatch as OnLower, while the new names may not be perfect, 
  I think they are better than the old ones.
  
- updated javadocs
- added copyright notice

  Strictly speaking, there is no need for copy-on-spawn because every
  change in the MDC already results in a copy of the hash map. Nevertheless,
  this change makes it easier for readers of the code to follow it.
  An external observer should not be able to tell the difference between the old and 
  the new code.
  

- doing integration tests with various databases for logback-access

  the tests to pass). Disabling the failing testDurationOfEnabledLog test
  on Linux.

Using ReadWriteLock  with the hope of improving performance.

- minor refactoring in DBAppender and related classes
- As suggested by John Gibson in LBCORE-15, we now use the prepareStatement method of 
  Connection which takes the sql statement followed by the autogenerateed key columnNames 
  (of type String[])

  This change is compatible with JDBC drivers of SQLServer and MySQL, as well as Oracle.

  JDBC drivers not supporting getGeneratedKeys are not affected by this change.

- added integration tests which are active only on my machine, namely, Orion. This avoids other
  developers from having to install Oracle, MySQL, Postgres and SQL Server just for the 
  logback tests to pass.
  
- similar tests on logback-access to follow.  

- renamed oracle9i.sql as oracle.sql  

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