[#534] Update configuration flags' documentation

Conflicts:

	doc/configuration.rst
[#534] Reorganize configuration flags' order in the docs
[#534] Add documentation for some configuration flags
[#534] Remove useless indexes in configuration page
[#534] Minor styling adjustements

Conflicts:

	doc/configuration.rst
[#534] Remove unused configuration flags
[#534] Document some undocumented config options

The added options are:

  ckan.tracking_enabled
  search.facet.limits
  ckan.root_path
  ckan.site_intro_text
[#534] Add E-mail Settings section and add cross-references to the config options.
[#534] Remove legacy config options

These ones are no longer used and will just confuse:

* package_form
* carrot_messaging_library
* amqp_hostname & amqp_port & amqp_user_id & amqp_password
* ckan.log_dir
* ckan.dump_dir
* ckan.backup_dir

Also some minor formatting fixes.

Conflicts:

	doc/configuration.rst
[#534] Rearrange sections and items

Sections rearranged by importance/usage and items put to their relevant
one.
Sections are now:

 *General Settings
 * Database Settings
 * Site Settings
 * Search Settings
 * Plugin Settings
 * Front-End Settings
 * Theming Settings
 * Activity Streams Settings
 * Feeds Settings
 * Internationalisation Settings
 * Storage Settings
 * Form Settings
 * E-mail Settings

Conflicts:

	doc/configuration.rst
[#534] Move authorization setting to config options docs

They are one of the most important ones and they should be found on the
conguration options docs. To avoid duplicating them the include rst
directive is used:

.. include:: /configuration.rst
   :start-after: start_config-authorization
   :end-before: end_config-authorization

This requires setting the two markers on the imported file, eg:

.. start_config-authorization

    ... stuff to include ...

.. end_config-authorization
[#534] Make reST labels for config settings consistent

Make the reST label for cross-referencing each config setting the same
as the name of the config setitng itself, e.g.
ckan.activity_streams_email_notifications, don't mix and match different
styles of ., _ and - like ckan-activity-streams-email-notifications,
ckan_activity_streams_email_notifications, etc.
[#534] Add reST labels to all config options

Now we can easily cross-reference any config option from any file in
docs/.
[#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
[#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