Clarified use of :sections: option in doxygenclass directive.
Clarified use of :sections: option in doxygenclass directive.

Found that properties were excluded by default.
kirbyfan64/breathe,kirbyfan64/breathe,RR2DO2/breathe,AnthonyTruchet/breathe,AnthonyTruchet/breathe,AnthonyTruchet/breathe,kirbyfan64/breathe,AnthonyTruchet/breathe,kirbyfan64/breathe,RR2DO2/breathe