Generate docs for config options.
Remove outdated config information
Start separating config docs into user and developer parts
Remove superfluous info on config system
Fix cross references from 0.11 whatsnew
Move editor config info into details.rst
Merge branch 'doc-config-options' into docs-refresh

Conflicts:
	docs/source/config/index.rst
Refer to options list in config intro
Rearrange index page of config docs
CSS tweaks to make definition lists look nicer
Fix width of search box
Refer to how to set config from options list
Fix some Sphinx warnings with autogenerated config docs
Describe CL precedence over config files
Mention that some options cannot be set through %config
Fix some whitespace, and use lisp highlightling for emacs code
Merge pull request #4492 from takluyver/docs-refresh

Configuration docs refresh

- Moved the technical details of the config system into the development directory.
- Added a new 'intro' document describing how to use the config system, without the technical info.
- Autogenerate lists of config options for the main components (this doesn't yet include the parallel machinery).
- Condense and tidy up other config docs, removing outdated information.