Split docs into siteadmin and pluginwriter guides

* create initial bits for plugin writer's guide
* move siteadmin stuff to site administrator's guide
* rework index.rst to support multiple guides
* tweak some text
* move files into subdirectories

I verified that this still works with html and texinfo build targets.
There's still a lot of work to do, but this is a good start.

docs/source/siteadmin/production-deployments.rst

@@ -0,0 +1,94 @@
+.. MediaGoblin Documentation
+
+   Written in 2011, 2012 by MediaGoblin contributors
+
+   To the extent possible under law, the author(s) have dedicated all
+   copyright and related and neighboring rights to this software to
+   the public domain worldwide. This software is distributed without
+   any warranty.
+
+   You should have received a copy of the CC0 Public Domain
+   Dedication along with this software. If not, see
+   <http://creativecommons.org/publicdomain/zero/1.0/>.
+
+=========================================
+Considerations for Production Deployments
+=========================================
+
+This document contains a number of suggestions for deploying
+MediaGoblin in actual production environments. Consider
+":doc:`deploying`" for a basic overview of how to deploy MediaGoblin.
+
+Deploy with Paste
+-----------------
+
+The instance configured with ``./lazyserver.sh`` is not ideal for a
+production MediaGoblin deployment. Ideally, you should be able to use
+an "init" or "control" script to launch and restart the MediaGoblin
+process.
+
+Use the following command as the basis for such a script: ::
+
+    CELERY_ALWAYS_EAGER=true \
+     /srv/mediagoblin.example.org/mediagoblin/bin/paster serve \
+     /srv/mediagoblin.example.org/mediagoblin/paste.ini \
+     --pid-file=/var/run/mediagoblin.pid \
+     --server-name=fcgi fcgi_host=127.0.0.1 fcgi_port=26543
+
+The above configuration places MediaGoblin in "always eager" mode
+with Celery, this means that submissions of content will be processed
+synchronously, and the user will advance to the next page only after
+processing is complete. If we take Celery out of "always eager mode,"
+the user will be able to immediately return to the MediaGoblin site
+while processing is ongoing. In these cases, use the following command
+as the basis for your script: ::
+
+    CELERY_ALWAYS_EAGER=false \
+     /srv/mediagoblin.example.org/mediagoblin/bin/paster serve \
+     /srv/mediagoblin.example.org/mediagoblin/paste.ini \
+     --pid-file=/var/run/mediagoblin.pid \
+     --server-name=fcgi fcgi_host=127.0.0.1 fcgi_port=26543
+
+Separate Celery
+---------------
+
+While the ``./lazyserer.sh`` configuration provides an efficient way to
+start using a MediaGoblin instance, it is not suitable for production
+deployments for several reasons:
+
+In nearly every scenario, work on the Celery queue will need to
+balance with the demands of other processes, and cannot proceed
+synchronously. This is a particularly relevant problem if you use
+MediaGoblin to host video content. Processing with Celery ought to be
+operationally separate from the MediaGoblin application itself, this
+simplifies management and support better workload distribution.
+
+Basically, if you're doing anything beyond a trivial workload, such as
+image hosting for a small set of users, or have limited media types
+such as "ASCII art" or icon sharing, you will need to run ``celeryd``
+as a separate process.
+
+Build an :ref:`init script <init-script>` around the following
+command::
+
+    CELERY_CONFIG_MODULE=mediagoblin.init.celery.from_celery ./bin/celeryd
+
+Modify your existing MediaGoblin and application init scripts, if
+necessary, to prevent them from starting their own ``celeryd``
+processes.
+
+.. _init-script:
+
+Use an Init Script
+------------------
+
+Look in your system's ``/etc/init.d/`` or ``/etc/rc.d/`` directory for
+examples of how to build scripts that will start, stop, and restart
+MediaGoblin and Celery. These scripts will vary by
+distribution/operating system. In the future, MediaGoblin will provide
+example scripts as examples.
+
+.. TODO insert init script here
+.. TODO are additional concerns ?
+   .. Other Concerns
+   .. --------------