Use AutoPtr in LoadParameterFile.cpp re #8546

Signed-off-by: Karl Palmen <karl.palmen@stfc.ac.uk>
Extend parameterXML code (still inactive) re #8546

Signed-off-by: Karl Palmen <karl.palmen@stfc.ac.uk>
Merge branch 'feature/8546_load_parameter_file_string' into develop