Enchanced/stats

[andrefbarros]

Feature: added new Grade calculator. Gives student the grade needed in the exam to obtain their objective in that specific UC)

• General styling fix in desktop or mobile
• Added more explanatory messages

When user do not fill the grade wanted

When user do not fill the frequency grade

When user wants a grade impossible to have according to the frequency grade

When user fills each field correctly

[ricardo177m]

Great addition!