[librep merge request] major doc revision

[Teika Kazura <teika lavabit com>]

Hi. Please merge my librep branch. It includes

* Major doc revision. 
Reorganized documentation files. Many capital letter name files are
updated or merged into the info.

New entries (Crash course for Elisp users, Closures, on leading tilde
in filename and tar archive access), fully revised the module section,
improved description on invocation, improved fluid and let
descriptions Module names are supplied for all functions.

Supplied documents to some functions.

See news or git log 4a3e91e2490..3f7a5aee3b1 for more

* define-special-variable is replaced by defvar-setq
In fact the former remains, but it's a very confusing name, so the
latter is introduced.

With best regards,
Teika (Teika kazura)