Refactor random fill to handle new multiple options changes

[tomaspalma]

Besides the act itself of generating random choices based on the available options, this issue is also aimed to the lock / unlock funcionality of an option, since that is part of the random fill.

Basically, if a course (disciplina) is locked, the <RandomFill> component ignores it and does not generate a random choice to that one.

In essence, in order to finish this issue, it should not be enough to just allow random courses to be picked when the user clicks the button. It should also handle lock / unlock logic.

Currently, the padlocks near the dropdowns to select a class option for a course are not correctly working and that is also part of the issue.