Implement document search

The document search selection type works now again. Due to missing
search engine it is of course far from good or practicable. The text
search of MongoDB seems to be questionable at the time being.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Add pry-rescue and pry-stack_explorer

I have added new pry extensions for debugging purposes.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Use the score to generate the pie chart

Designing one generic view for very different metrics is a difficult
task and I do not want to invest too much time into this topic. For now
I have made the pie chart a little bit more general by showing the score
distribution of the score value.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Style pie chart for score distribution

The pie chart is now nicely positioned in its own dashboard. I have also
added an individual dashboard rule for this.

Signed-off-by: Konrad Reiche <konrad.reiche@gmail.com>
Remove text out of pie chart

Just removed the text labels out of the pie chart. This makes a lot more
readable if values have too long texts, etc.

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