Remove calendar and add tutorials to the menu

[Mouvedia]

No description provided.

[Ragnis]

Firstly, these are two completely different problems and they should be
submitted as separate issues.

The calendar will not be removed, but it probably will be soon replaced
with something better (more on that later).

Obviously I can not add the tutorials directly to the menu. The
tutorials will be listed on our "Resources center" page (issue #349).
Some recent tutorials will also be shown on our front page as shown
here

I am now closing this issue.