Edits in response to public comments 2021-06-28 through 2021-07-09 (#2)

* Update BEDv1.tex

* polished edits

* Edits in response to public comments 2021-06-28 through 2021-07-09

* Edits in response to public comments 2021-06-28 through 2021-07-09 fix typo

* Edits in reponse to GA4GH PRC

* line edit

* Edits in response to public comments 2021-07-09

* further line edits and footnote fixing

* fix texlint issues

* WIP address uninformative/default/empty issues

* fix empty/uninformative issues

* clarify language on BED fields not being empty

* add special-case `diff/BEDv1.pdf` target that uses lualatex

Co-authored-by: Michael Hoffman <[email protected]>
Co-authored-by: Jeffrey Niu <[email protected]>