gitweb.js: Update and improve comments in JavaScript files

This consists of adding a few extra explanation, fixing descriptions
of functions to match names of parameters in code, adding a few
separators, and fixing spelling -- while at it spell 'neighbor' using
American spelling (and not as 'neighbour').

This is post-split cleanup.

Signed-off-by: Jakub Narebski <redacted>
Signed-off-by: Junio C Hamano <redacted>