Improve pop-up on Evaluation Table

[SepsiLaszlo]

The EvaluationsController's table view has a pop-up that can be opend with the Help Me button.
We should open this pop-up for every user when they visit the page at the first time.
Tha application should keep track of which users visited the page in the database.
The goal is to help users find information about how the evaluation system works.