build script inside logback-example/pom.xml create the lib directory.

- added test cases in relation wit ContextPropertyConverter

  Implemented as 
  
  if(le.hasCallerData()) {
    ledo.callerData = le.getCallerData();
  }
  
  as (correctly) suggested by Joern Huxhorn
- added  test case as appropriate

  The following config files will be interpreted identically:

First config file:
   
<configuration>
  <logger>...</logger>
</configuration>

Second config file:

<CONFIGURAtion>
  <loGGer>...</loGGer>
</CONFIGURAtion>
  
  This addresses http://jira.qos.ch/browse/LBCORE-76

- improved docs on TimeBasedRollingPolicy

- added blurb about LBCORE-90 being fixed

  This eliminates the need to slashify regular expression at a later time 
  (since the original pattern is already slashified)
- While cleaning archived log files, empty fodlers are taken into account, especially if
  they are in cronolog-style "/var/tmp/2009/08/04/foo.log". 
- old archives are cleaned for time-based triggering as well as size-and-time-based triggering
- relevant test cases

- The TimeBasedCleaner class was refactored into the ArchiverRemover interface and DefailtArchiverRemover class.
- Providing an archive cleaner is now a responsibility of any TimeBasedFileNamingAndTriggeringPolicy

- code needs some refactoring but essentially seems to work

- added a few comments