Use jinja2 templates, various fixes.

Now I create an index page for the html status pages we generate; also
some corrections to provision.sh and other parts of the scripts have
been implemented. The code is now slightly less ugly, and it happily
runs in labs.

Change-Id: I6a70c5fdea282f3922bdf9c4012e9ea09d8c1a75
Signed-off-by: Giuseppe Lavagetto <glavagetto@wikimedia.org>