Improve existing metrics in 'Project page' using Bokeh

This epic is to improve the existing metrics on a project page. There are 2 basic aspects to discuss:

• On the one hand we have to know the limits of Bokeh, try the different ways to obtain the data, create a dashboard with graphs using the same date range, etc.
• On the other hand, we have to discuss the metrics that we are going to include. Average time to close issues, activity evolution charts, number of authors, etc.

Closing condition: a complete dashboard in the project page with useful metrics related with the project and include filters for all the visualizations (e.g. time picker).