[REFACTORING] rename field
remove the field "required"
add a node class for all the single value nodes
add a parser of config xml file
add a node class for "general"
add a node class for "target"
remove format checking of XML file
add a node class for "clone-detection"
add a node class for "mapping"
add a node class for "common-configuration"
add a node class for "strategies"
add a node class for "strategy"