fix the XML again
use consistent terminology for header field
Merge initial tables (#259).

Changes:
- Add :method:POST
- Remove :host:
- Add host:
- Add :authority
- Sort order
  - First header fields with non-empty values
  - Second header fields with empty values (alphabetical order).
Consistent use of header fields.

Add "field" where missing after header.
Make initial header table always accessible.
Add change log.
Add reference to HTTP/2.0.
Insert headers at '0' (#233).

Change the location of inserting and removal of headers into the header
table.
Consistent use of header fields.
Remove headers from static table.

Remove:
- connection
- transfer-encoding
Remove header name lowercasing.
Clarity fix.
Reformat
Remove IANA consideration.
Merge pull request #276 from jpinner/header_field

use consistent terminology for header field
Add figure for header table.