[tldistro] directories customization [help cmd]

[Karl Berry]

    And most importantly, in the install-tl tool when I select HELP <H>,
    I get an error (no help file ?) 

Turns out the H(elp) command has not worked for years. And all it did
was dump to stdout the html that's online at
https://tug.org/texlive/doc/install-tl.html, which does not seem very
readable or useful.

So I removed the H command and instead added the above url to the
"banner" that's printed out at the beginning of the main menu:

======>   Letters/digits in <angle brackets> indicate   <=======
======>   menu items for actions or customizations      <=======
= help>   https://tug.org/texlive/doc/install-tl.html   <=======

Thanks for the report. -k