Update README.md (#1270)

Round 2 of updaing readme.

fixed, designed and repositioned "Supported Feature" section
Added dividers between features in features section
added API column to the quantization methods table
added links to relevant notebooks in relevant places
made images of tasks (under results) a bit smaller
Fixed Headers issue (some headers were in wrong level.)
added more capabilities under debug feature - Xquant & network editor (including links to tutorial
centered all section titles (makes the page more clean in my opinion)
fixed according to review:
-- - added tutorials to qadvanced quatntization & Quantization parameter search.
-- - Updated EPTQ paper title and added E. Cohen as contributer
-- - changed type (on the how to -> on how to)