reRoyalBlood tweaks, V.missingTable typing, and helper functions

This implements the first suggestion in #5549

Changes

• FC.MissingParentRecord type which is applied to V.missingTable
• Added missingTableRecordFromHumanState() which makes a valid FC.MissingParentRecord object when given a HumanState object
  • Replaced code with missingTableRecordFromHumanState() where it made sense
• Added generateMissingParentID() which decrements V.missingParentID and makes sure it isn't already in use for some reason and then returns a unique (to V.missingTable) id
  • Replaced code with generateMissingParentID() where it made sense
• App.Events.RERoyalBlood now generates the king and adds it to V.missingTable if the queen and/or either of her children are acquired
• If the pregSource is in the missing table and V.showMissingSlaves === false we will now show an unknown father's growing ... instead of undefined's growing ...
• The king is now shown as the parent of the queen's fetus as long as V.showMissingSlaves === true, otherwise it shows an unknown father
  • This is the existing behavior. @Pregmodder It may make sense to set V.showMissingSlaves === true as the default for new games at this point in time