Juror coherence score and level computation

[jaybuidl]

To be integrated on #264

Coherence score

score goes from 0 to 100

score = 100 * number of coherent votes / (number of votes + smoothing factor)
if number of votes == 0 then score = 0

smoothing factor = 10

Level

Coherence score	Level	Title
0 <= score < 20	0	Diogenes
20 <= score < 40	1	Pythagoras
40 <= score < 60	2	Socrates
60 <= score < 80	3	Plato
80 <= score	4	Aristotle