don't use link abbreviations

It's unnecessary indirection when there aren't multiple links to the
same site.
rename manual.org to index.org
convert old rst manuals to org mode

This is just the initial conversion with pandoc, they still need to be
fixed up. Also define new org files as a project in yas-doc-helper.el.
split symbol reference into separate file
move index.org subsection into snippet-organization.org

This almost completely overwrites the existing snippet-organization.org
which was imported from snippet-organization.rst via pandoc.
fix links
move index.org subsection into snippet-expansion.org
link to docstring ref; fix other links, formatting
move images to the section they describe
replace obsolete refs

yas-trigger-key -> bind yas-expand
yas-mode-symbol -> call yas-activate-extra-mode
add code examples for snippet-expansion.rst

pandoc org -> rst drops them
more links to docstrings, don't repeat docstrings
snippet-menu.org: links, formatting, obsolete refs
{snippet-development,faq}.org: fixup pandoc output

- add source blocks
- fix links
- don't duplicate docstrings
- formatting
remove erroneous #+BEGIN/END_QUOTE

pandoc decided to add those for some reason
move top heading to title

and all the other headings one level up. Except for
snippet-reference.org; yas--document-symbols doesn't quite work right in
that case, fix it later.
move #+STARTUP to org-setup.inc; add #+LINK_HOME

also remove #+AUTHOR since it ends up refering to the generator, not the
actual author.
publish org doc from Rakefile
retrieve function documentation correctly
fix docstring extraction for "fancy" docs

The docstrings for yas-expand and yas-expand-from-keymap are generated
on the fly, depending on how they are called ("context"). Add a context
argument to the synthesizing functions and pass it nil when extracting
docstrings for the manual.