Better handling of linkage type and status

[ric2016]

PEDIGREE_LINKAGE_TYPE:= [ adopted | birth | foster | sealing ]
CHILD_LINKAGE_STATUS:= [challenged | disproven | proven]

both should be handled:
minimally change displayed relationship name;
maybe don't use for relationship calculations at all, or make this configurable: E.g. exclude adopted/challenged/disproven ...

See also
fisharebest/webtrees#1236

[ric2016]

Partly handled in #36 (pedigree). Child linkage status should be easy to add to direct relationship names now as well.