add default constants for XMLConfigurationService
fix up comments
throw more specific Exceptions
slight formatting changes
move MBeanAttribute and MBeanHolder to their own file
Revert "add default constants for XMLConfigurationService"

This reverts commit 78fb5c7566a22c9b30eaeeb1198c85e2e6d0297e.
simplify configuring of command line parameters
formatting fix
Move construction of MBeanAttribute to its own method.

Also includes minor changes in formatting.
fix constructor params order of MBeanAttribute
split up configureFromXml method
move constants declaration to start of class
introduce new class CommandLineArgs
move CommandLineArgs to new file
tweaked the way selectParameterFromNode works
rename methods to clarify role
remove stray debug message
Slight changes to configureGangliaFromXml for readability
Remove stray TODO
Slight refactor of XPath methods for readability