measurement-class: make owner member more clear

Signed-off-by: Hagen Paul Pfeifer <hagen@jauu.net>
doc: add module documentation

Signed-off-by: Hagen Paul Pfeifer <hagen@jauu.net>
doc: add section note to module documentation

Signed-off-by: Hagen Paul Pfeifer <hagen@jauu.net>