(issue GH-7)some typos and formating touch ups

Validation: all Q&A between the two presentations have the same answers
exception: BG 3 is totally different than EN 3 (still)
(issue GH-7) remove english txt from BG 12 answer
(issue GH-7)fix BG 20 question typo: Pearl -> Perl
(issue GH-10)more links for question 18
(close GH-7) translate to BG question 3
(issue GH-10) fix/add links for 1, 2, 5, 10, 16...
(issue GH-9) fix typo: Vectorial -> vector