harmonize all plugins docs

Add a configuration section that lists all options for each plugin.
List options in alphabetic order.
Mention the default value for each option.
Use same sentences to describe concepts common to different plugins eg 'auto
option, install description
docs: add plugin name in "how to configure" sentences
docs: remove space before colon
fix typos
fetch art doc: restore section title
fix index toc
changelog.rst: remove links to echonest_tempo
always a colon between the option name and the rest of the description

plus typos and case change
Plugin docs overhaul tweaks through "duplicates"

Moving alphabetically through the docs. Got a long way to go...
Refresh without scrolling to top
make auto: Ignore "deleted" events

vim's atomic writes delete the file and then re-add it, which was leading to
Sphinx being triggered twice.
Docs cleanup through ftinitle
Finish the pass over all plugin docs
Typo fixes
docs: make Travis happy
Merge pull request #1047 from sampsyo/docs_overhaul

Docs overhaul