Dashboard: Add pagination to the family list on the frontpage

[felipesanches]

We're now dealing with almost a thousand font families. This is too much to show at once at the dashboard front page, so it would be good to add a pagination system to show just a few families per page. Maybe 50 or so...

[davelab6]

The webapp still available from http://fontbakery.com dealt with this already, with some nice lazy-loading code. I hope you can use it :)

[felipesanches]

Migrating to fontbakery-dashboard issue tracker per #1383