Use hyphens for unknown scores in the leaderboard

Instead of zero hyphens are now used for repository (snapshot) scores
where the score is not known yet. Also unknown scores are not used as
a penalty in the total score, but simply ignored.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Preserve words which would be eliminated otherwise

There is a special case with short texts in the richness of information
metric. In one dataset the description text was a year range. Due to the
splitter regular expression the whole text is eliminated.

This should be revisited at another time. Especially, multiple appliance
of the word tokenizer should not alter the output more than once.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Make custom weighting part of the repository model

Since the sort method needs to access the weighting, as well, I cannot
simply pass it through the method. I added a class variable which is
updated every time the weighting is updated.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Rotate metric names in the leaderboard table

The rotation makes the whole table more lively. Not only do the metric
names now stand out, but there is more space for their sometimes lengthy
names.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Add New Relic again for test on production

Maybe the New Relic plugin did not work, because it is only designed to
work on production servers. I give it another try.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Design landing page

This is the first landing page design. I have added several screenshots,
made the layout independent of the general layout and made a lot of
custom fixes on the stylesheet.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Improve the quality distribution view

The view selected through the charts delivers now, the identifier, name,
score and URL pointing to the API of metadata records from a particular
quality distribution group.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>