Add non-active parameterXML property re #8546

I also drilled it down into the execManually method changing its arguments.

Signed-off-by: Karl Palmen <karl.palmen@stfc.ac.uk>
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>
Activate new code and remove unneeded AutoPtr re #8546

Signed-off-by: Karl Palmen <karl.palmen@stfc.ac.uk>
Check file and string property re #8546

At least one of these two properties must be set.

Signed-off-by: Karl Palmen <karl.palmen@stfc.ac.uk>
Add unit test to test new property re #8546

Signed-off-by: Karl Palmen <karl.palmen@stfc.ac.uk>
Add test for absence of file or string re #8546

Also correct the error message.

Signed-off-by: Karl Palmen <karl.palmen@stfc.ac.uk>
Add reference to ticket #8521 in comment re #8546

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