Adding to lexicon; removed extraneous header ids.
Merge branch '6.1.x' into 6.1.x-latex
Added advanced web content keywords to lexicon
Updated lexicon.
Lexicon up through chapter 8.
Lexicon up to chapter 9.
Lexicon up through Chapter 10.
Lexicon up through Chapter 12.
Lexicon up through Chapter 13.
Lexicon through Chapter 14.
Lexicon up to chapter 15.
Lexicon up through Chapter 16.
Lexicon through Chapter 17.
Lexicon up through Chapter 18.
Lexicon through Chapter 19.