Support entity references in propositions

[carlgieringer]

Counter propositions frequently need to refer to a Source or sometimes a Proposition. This is because they are either critiquing the Source's relevance or the Proposition's relevance on the basis of relevance.

Examples:

• "Kirk updated his Quora answer to say that the height limit in D.C. is not based on the Capitol" countering the Source Kirk Janowiak's answer to Why doesn't Washington DC have any high rise buildings compared to most American cities of a similar size? - Quora.
• The PRI article "Sweating is an essential and uniquely human function" is based on an interview that issued a retraction for the statement that "humans are the only mammals that sweat" (also see justifications for that Proposition.)
• Descendants of https://www.howdju.com/p/1865/a-strain-of-h1n1-swine-flu-was-the-first-known-example-of-a-virus-created-by-serial-passage-leaving-a-lab
  • https://www.howdju.com/p/1870/the-paper-kozlov-j-v-gorbulev-v-g-kurmanova-a-g-bayev-a-a-shilov-a-a--zhdanov-v-m-1981-on-the-origin-of-the-h1n1-aussr9077-influenza-virus-journal-of-general-virology-56-437-makes-it-just-beyond-doubt-that-the-aussr9077-strain-of-the-influenza-virus-h1n1-was-subject-to-serial-passage
  • https://www.howdju.com/p/1872/the-paper-kozlov-j-v-gorbulev-v-g-kurmanova-a-g-bayev-a-a-shilov-a-a--zhdanov-v-m-1981-on-the-origin-of-the-h1n1-aussr9077-influenza-virus-journal-of-general-virology-56-437-never-mentions-serial-passage