Typographical nits (SOAP, editorial)

- Section 3.3, first bullet: "each [reference parameter]" -> "each of 
  the [reference parameters]"

- Example 5-1 says "<!-- Headers elided for clarity.  -->" The correct
  word is probably "brevity".

- Example 5-2 is the only SOAP 1.1 example, yet it doesn't show any WSA
  headers.  It might be worth losing brevity to have one example of a 
  SOAP 1.1 envelope containing at least the WSA headers shown in 
  Example 5-1.

- Section 5.5 "xs:NonNegativeInteger" -> "xs:nonNegativeInteger"