Support Proposition relations

[carlgieringer]

• Possible relations (see here, here, and here):
  • equivalent (two Propositions are semantically equivalent and could be consolidated)
  • anti-equivalent (two Propositions imply the falsehood of each other.)
  • suggested/preferred alternatives (See also Support truer alternative proposition based justifications #34)
  • related: users interested in one Proposition may be interested in the other.
  • “Often confused with”
  • Contains/IsContainedBy?
  • MoreGeneral/MoreSpecific?
• Support adding and voting on the relations
• Support jobs for aggregating the votes
• Support displaying equivalent propositions, combining their justifications, and separating the justifications if a user votes against it.
• Support inferring justifications from anti-equivalents
• Support jobs combining/separating justifications