[#534] Edit top of configuration docs page

Use the default ini file locations; Clarify what the [app:main] section
is; say "restart webserver" not Apache, webserver may not be Apache.
[#534] Use .. deprecated:: in config docs
add a helpful response to SearchIndexError exceptions raised within the action api
[#751] Edit the release cycle docs
Merge branch '751-release-docs'
[#838] Postgres error codes are five character strings, not integers
Merge branch '838-pgcode-string'
Merge branch '827-ga-fix'
[#531] Update data viewer docs
Merge branch '824-flags'
[#808] Fix unicode template 500 error
[#535] Remove errors that aren't valid anymore
[#534] Document ckan.template_title_deliminater
[#534] Calm down over-the-top warning
[#534] Fix some formatting issues in the docs
[#534] Docs correction: template_footer_end is not legacy

Appears in jinja templates
[#534] Update ckan.site_url docs

This is used by much more than just the API
[#534] Typo
[#534] Docs: correct default value fopr ckan.cache_expires
[#534] Correct ckan.page_cache_enabled

Fix typos, and mark the feature as experimental