lot of newbie questions

[toto@tots-ns.net]

Hello list, I've got a lot of newbie questions. I'm writing a technical 
document with context for the first time to try it. I come from a 
TeX/LaTeX world.

-> How to print a tilda? I'm trying to write an URL with a tilda in it 
with the font \tt. \widetilda, \tilda do not output any character. Even 
\~{} do not print anything. And it does not seem to appear somewhere in 
the wiki or in the "special characters" section of the "ConTeXt an 
excursion" excellent document.

-> How could I do french guillemets (<< and >>)? Is it possible?

-> I would like to make a glossary, ie an index with a definition for 
each entry. Many parts of the manual could help me but i don't really 
now in which direction to dig: is it a list of definition? Should I use 
registers?

-> I'm trying to put a metapost graphic in the margin like te example 
in the manual reference (page 47) using the following command:
\definestartstop[important][command={\inmarge{\useMPgraphic{bang}[width=\marginwidth]}}]
But (of course :) it does not work at all and put some blank pages. Any idea?

Thanks a lot for your help. And thanks a lot to all the developpers od 
ConTeXt: it is thought in a really smart way!

-AJ