[RFC] get-deps.sh make-over

I would like to make get-deps.sh a little more informative.

1) every time it downloads something, it should tell you what it got,
where it is and what it's needed for and what you're expected to do
with it, if anything.

For example:

- downloading apt (required library) from ...
- done -- <pointer to complex instructions>
-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
- downloading Serf (optional library) from ...
- renaming directory
-- done -- <simple instruction what to do next>
....

2) if it doesn't download something it should tell you what there is,
if possible, e.g.

-- Serf 1.1.1 already present in trunk/serf/

3) A more informative --help output that introduces get-deps.sh, with
subcategories that display the help for the downloads, e.g.
./get-deps.sh help serf
  <instructions regarding how to proceed with serf after download>

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Comments?
Gabriela