Add the statistics encouragements to the homepage

We want to add some sort of encouragements model to the homepage. Something that checks the statistics and says something like "Only X amount of people using this app have ever managed to go this far as you ahve! Nice works!"

or : "X% of our users have also gotten this far in their treatmentplans! Good work! "

or something similar

Start at the homepage entry point and trace how treatment-plan statistics are made available there. Define the encouragement rules, wording, and handling for the available statistics before implementing them; done means the homepage displays an appropriate encouragement based on user progress.

Written by the indexing model from the issue text.