anchor.diff:  As convenience the following base classes are provided:
   
   * +org.apache.tamaya.mutableconfig.spi.AbstractMutableConfiguration+ simplifying implementation of +MutableConfiguration+.
  -* +org.apache.tamaya.mutableconfig.spi.AbstractMutableConfigurationBackendSpi+ simplifying the implemenation of
  +* +org.apache.tamaya.mutableconfig.spi.AbstractMutableConfigurationBackendSpi+ simplifying the implementation of
     +MutableConfigurationBackendSpi+.
positive.code:       .commit();
  --------------------------------------------
  
  Hereby it is also possible to provide multiple URLS that allows you to write your configuration chnges back to multiple
  backends in one go. Also be aware that the effective effect of your changes to the overall configuration changes cannot
  be easily predicted, since it depends on several aspects:
  
  . is the corresponding configuration resource configured as part of the current system's configuration?
  
negative.code: [source,java]
  .Checking for mutability
  --------------------------------------------
  MutableConfiguration config = Configuration.EMPTY.query(
      MutableConfigurationQuery.of("file:/home/etcd/backup-config.properties");
  
  if(config,isWritable("mycluster.shared.appKey")){
  