Add colour code or label to blood related persons

[hartenthaler]

Besides the sex of a person, the status of a shown person regarding blood relationship is important. It would be nice to easily identify blood-related persons by a colour or a label (maybe including the percentage of blood relationship).

Showing this for a whole block, as it is now, is not enough, because in a block there are maybe parents and step-parents together.

To check whether there is a blood relationship it is necessary to check against all biological parents and their biological descendants of the proband.

[hartenthaler]

see similar function "checkRelationship" in FancyTreeviewModule.php