Updates to CAPTCHA doc - impacts CfC to publish

I've pushed a bunch of changes to the CAPTCHA document prior to 
publication, that I believe are all editorial, but are somewhat substantial.

The biggest one to note is the abstract rewritten. The previous abstract 
seemed to me to have too much values language in it (the word 
"pernicious" was a clue to that), and it presumed background knowledge 
we shouldn't assume readers have. The abstract is mean to be a 
high-level overview of the document, and is automatically pulled into a 
number of places, so even if we plan to edit later, it could be too late 
to avoid certain problems if we don't address prior to the first public 
working draft. I believe my wording is more neutral in tone and 
adequately introduces the document.

The other noticeable change is with references. The document mainly used 
a format like "This is discussed in [XMLName]" whereas the W3C Manual of 
Style (https://www.w3.org/2001/06/manual/#References) says the format 
should be "This is discussed in Namespaces in XML [XMLName]" to 
introduce the reference during the reading flow. I had to make 
judgements about how to incorporate these into the prose, but think it's 
still editorial.

Some references I turned into ordinary links, not bibliography entries. 
In general, when citing a source, we should use bibliography references, 
but when just referring to a site or product, a simple link is sufficient.

Another change I had done before opening the CfC to publish, but forgot 
to merge until after the CfC opened, was to add a list of terms as an 
appendix. Janina had given me the terms and some pointers towards 
definitions; I did my best to construct sensible definitions of the 
terms. I was unable to find definitions for "hot word" and 
"polymorphism", so those are commented out.

Finally, this document was proposed as a version 2, but because it's a 
Working Group Note, it doesn't really make sense to version it and leave 
the old one floating around, as we can simply update the note. So I 
change the title and shortname so it will simply the old version. The 
previous version will still be accessible by dated URI, but the new 
publication will update the URI https://www.w3.org/TR/turingtest/ 
immediately, though indicating it as a Working Draft, not a Note until 
it advances again to that status.

I believe the rest of the changes are clearly editorial. If you have 
concerns about any of these changes with respect to the documents 
approval to be published as a First Public Working Draft, please let us 
know.

Summary of changes:

  * switch to software license since Note track
  * update copyright year
  * genericize product name
  * square to curly quote conversion
  * replace quoted titles with cite
  * lower case bibrefs
  * bibref cleanup
  * spell check
  * abstract rewrite
  * remove redundant
  * comment out terms we don't have defs for
  * capitalization
  * definitions for most of the terms
  * first pass on terms from Janina, some of them references instead
  * update funder acknowledgement to maybe or maybe not the right one
  * split new and old acknowledgements
  * retitle introduction
  * remove unnecessary IDs
  * character entity fix
  * add subtitle
  * unmark as version 2
  * reference previous note
  * add Matt May as former editor