Link to docker support from main web index. Docker support changes.

With link from main web page going to docker support, add published
docker image link and link to tags to the first paragraph to the
Docker Support section.

Some minor clarification of workding for docker tags. Typo fixes.

Author: rouilj

doc/installation.txt

@@ -1618,18 +1618,23 @@ Docker Support
 ==============
 
 If you don't want to install Roundup on a host, you can create a
-Docker container. This installs Roundup using the `stand-alone web
-server`_ method. This image only supports http. We suggest putting an
+Docker container or use the `pre-built container on
+hub.docker.com
+<https://hub.docker.com/r/rounduptracker/roundup>`_. Docker hub
+images support `multiple tags <#tags-for-dockerhub-docker-images>`_.
+Docker images run Roundup using the `stand-alone web
+server`_ method. The image only supports http. We suggest putting an
 https terminating proxy in front of it.
 
 This is a work in progress and patches to improve it are welcome. You
 can find the docker config files under the `scripts/Docker` directory
 of the source tree.
 
-The dockerized Roundup is based on a 64 bit Alpine distribution.  It
-includes database drivers for anydbm, sqlite, MySQL and Postgresql
-(Postgresl is untested). It also includes additional libraries that
-are listed in `scripts/Docker/requirements.txt` (including redis).
+The Roundup container uses the 64 bit Alpine Python distribution.
+It includes database drivers for anydbm, SQLite, MySQL and
+Postgresql (Postgresql is untested). It also includes additional
+libraries that are listed in `scripts/Docker/requirements.txt`
+(including redis client support).
 
 Email support is a work in progress. Outgoing email to an external
 SMTP server should work. Receiving email should work by using a
@@ -1935,8 +1940,10 @@ releases (not pre-releases) are tagged this way. For example, the
 tags when 2.3.0 is released will be:
 
 ``rounduptracker/roundup:latest``
-   is a moving tag that tracks the latest build
-   with the newest version of Roundup.
+   is a moving tag that tracks the latest build with the newest
+   production version of Roundup using the current newest Alpine
+   release with the versions of Python packages at the time of
+   the build.
 
 ``rounduptracker/roundup:2.3.0``
    is a moving tag that tracks the latest build
@@ -1959,12 +1966,12 @@ example: ``rounduptracker/roundup:2.3.0b1-devel``,
 ``rounduptracker/roundup:devel``
 
 You should not assume that any ``devel`` tag is static. They are
-mainly for use by Roundup developer/maintainer for testing. There
-may be alternate tags ending with ``-devel`` to indicate builds
-from specific Mercurial versions/hashes. Also the tag may be
-overwritten to change the underlying Python libraries or
-images. Unless you like the bleeding edge, these should not be
-used in production.
+mainly for use by Roundup developers/maintainers/testers for
+testing. There may be alternate tags ending with ``-devel`` to
+indicate builds from specific Mercurial versions/hashes. Also the
+tag may be overwritten to change the underlying Python libraries
+or images. Unless you like the bleeding edge, these should
+**not** be used in production.
 
 Maintenance
 ===========

website/www/index.txt

@@ -185,8 +185,8 @@ Follow the source gratification mode with these steps (change the
 3. ``cd roundup-2.3.0``
 4. ``python3 demo.py``
 
-(The source download can also be used to create a custom Docker
-image.)
+(The source download can also be used to `create a custom Docker
+image <docs/installation.html#docker-support>`_.)
 
 Alternatively, you can install using a virtual environment with pip
 by: