Doc-fr: updates LM, NR, Usage, Extending and Web
Doc-fr: updates texidocs
Doc-it: fix credits for translation checkers

I want to keep track of translated files that still need a review
from a translation checker. And I don't want someone to be credited
for something he never did.
Doc-it: add chapter 1.4 of Notation Reference
Web-fr: updates browser-language

according to latest Firefox
Issue 3421: Percent signs in ghostscript output files should be duplicated
Make format for key changes consistent; minor formatting corrections for affected regtests
Updates to NR chapter 5
Updates to NR sections 3 and 4
Adds version number to web page side bar (Issue 3367)
Merge branch 'master' into translation
Issue 519: Warn about cross-platform font inconsistencies.
Issue 1168: website graphical design

On the website home page:
  Center the `squiggle' graphic.
  Add vertical space between news posts.
Issue 3190: Fix W3C compliance.

Fix incorrect nesting of tables in `Manuals' section of
  Community > Development on website.

Adjust css rules as needed.