extracted QUIZ and DICTIONARY global objects
corrected select query (changed joins to left joins)
renamed dictionary_quiz.html to quiz.html
corrected select query
refactored dictionary.js: added message to string auto conversion in echo_message function, added isStrEmpty function
refactor in quiz: added generateForms function (first draft)
added paragraphs and attributes names in quiz generation
adjusted quiz generation and answers check functions
added distinct to group_concat clauses (it was doubling results)
Merge branch 'feat/quiz-rebuild' into develop