rm unused packages folder
tweaks to links on packages section
add anchor to around-web
Add slides & videos on the "Learn" page.

Yaron's "Effective ML" on the documentation page was replaced as it
now appears on the "Learn" one.
Add a title to the mailing list page.
Only leave targets needed by Makefile.from* in Makefile.common
Add a "type" to the shortcut icon link.
Merge remote-tracking branch 'origin/redesign' into redesign
Extend the CSS trick so that <h1 id>,... do not fall under the nav. bar.
Merge remote-tracking branch 'origin/redesign' into redesign
Put the headers behind the text.

The trick to make headers anchors appear below the nav. bar enlarge
the (transparent) box containing the title.  This box covers the text
and may prevent from clicking links.  This commit fixes that problem.
Do not add a <p> to each item of the tutorial list.
Merge remote-tracking branch 'origin/redesign' into redesign