Pass of abstract, intro, and references

[cjpatton]

Make the terminology in the intro more consistent with the rest of the document, e.g., say "measurement" instead of "input".

For the references (cf. https://github.com/cfrg/draft-irtf-cfrg-vdaf/pull/508):

• Use "refcontent" instead of "seriesinfo" for conferences
• Use "name" instead of "ins" with the authors' full names as they appear in the references
• Harmonize ordering and date format

Tidy up the presentation language section:

• We want to say "encoding and encoding of messages as bytes strings are as in RFC8446", but for some reason we say this into the second to last paragraph, between two exceptions to RFC8446 we want to document. Move this language up to the first paragraph.