Micro-optimization for browsing experience, part 2.

[+] Changed preference 'general.smoothScroll'  boolean value from true to false.
[!] Preference 'mousewheel.min_line_scroll_amount' should be set from 5 to 40.
[!] Preference 'image.mem.min_discard_timeout_ms' should be set from 10000 to 1050000000.
[!] Preference 'image.mem.max_decoded_image_kb' should be set from 51200 to 512000.
[!] Preference 'general.smoothScroll.pages' boolean value should be set from true to false.
[!] This commit aims to improve browsing experience, on sites such image galleries like DeviantArt, Pixiv, etc.