remove docgen remnants from repo, update CHANGELOG

utils/apidoc/mdn/README.txt

-***** Current status
-
-Currently it runs all the way through, but the database.json has all
-members[] lists empty.  Most entries are skipped for "Suspect title";
-some have ".pageText not found".
-
-Currently only works on Linux; OS X (or other) will need minor path changes.
-
-You will need a reasonably modern node.js installed.
-0.5.9 is too old; 0.8.8 is not too old.
-
-I needed to add my own "DumpRenderTree_resources/missingImage.gif",
-for some reason.
-
-For the reasons above, we're currently just using the checked-in
-database.json from Feb 2012, but it has some bogus entries.  In
-particular, the one for UnknownElement would inject irrelevant German
-text into our docs.  So a hack in apidoc.dart (_mdnTypeNamesToSkip)
-works around this.
-
-***** Overview
-
-Here's a rough walkthrough of how this works. The ultimate output file is
-database.filtered.json.
-
-full_run.sh executes all of the scripts in the correct order.
-
-search.js
-- read data/domTypes.json
-- for each dom type:
-  - search for page on www.googleapis.com
-  - write search results to output/search/<type>.json
-    . this is a list of search results and urls to pages
-
-crawl.js
-- read data/domTypes.json
-- for each dom type:
-  - for each output/search/<type>.json:
-    - for each result in the file:
-      - try to scrape that cached MDN page from webcache.googleusercontent.com
-      - write mdn page to output/crawl/<type><index of result>.html
-- write output/crawl/cache.json
-  . it maps types -> search result page urls and titles
-
-extract.sh
-- compile extract.dart to js
-- run extractRunner.js
-  - read data/domTypes.json
-  - read output/crawl/cache.json
-  - read data/dartIdl.json
-  - for each scraped search result page:
-    - create a cleaned up html page in output/extract/<type><index>.html that
-      contains the scraped content + a script tag that includes extract.dart.js.
-    - create an args file in output/extract/<type><index>.html.json with some
-      data on how that file should be processed
-    - invoke dump render tree on that file
-    - when that returns, parse the console output and add it to database.json
-    - add any errors to output/errors.json
-  - save output/database.json
-
-extract.dart
-- xhr output/extract/<type><index>.html.json
-- all sorts of shenanigans to actually pull the content out of the html
-- build a JSON object with the results
-- do a postmessage with that object so extractRunner.js can pull it out
-
-- run postProcess.dart
-  - go through the results for each type looking for the best match
-  - write output/database.html
-  - write output/examples.html
-  - write output/obsolete.html
-  - write output/database.filtered.json which is the best matches
-
-***** Process for updating database.json using these scripts.
-
-TODO(eub) when I get the scripts to work all the way through.