extends PR26 to address issues with web root

[Paraphraser]

docker-entrypoint.sh altered:

1. The www folder in the base image is used to non-destructively populate the www folder in the persistent store.

   templates is a sub-folder of www so it is included in the copy.

2. The following additional argument is passed to domoticz when it is launched by docker-entrypoint.sh:

   -wwwroot /opt/domoticz/userdata/www
   

   This causes domoticz to use the copy of the www folder in
   the persistent store.

3. More consistent use of environment variables rather than duplicated path names.

[Paraphraser]

Shows:

1. domoticz process being passed -wwwroot argument.
2. Responding properly to curl (IOTstack service definition for domoticz maps external port 8083 to internal port 8080).

Shows browser connecting successfully.

[Paraphraser]

Further to the latest commit, given:

$ tree ./volumes/domoticz/templates/
./volumes/domoticz/templates/
├── angular.example
├── custom.example
├── custom.html
└── readme.txt

where custom.html is a copy of custom.example, plus enabling "custom" in the user menu:

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Also, the commit message seems to have lost some titles. The original markdown follows below (should be more readable).

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It occurred to me that, although bulk-copying the entire www folder to the persistent store "worked", it was probably storing up trouble for the future. In particular, if changes were made "upstream", those would not get copied to the persistent store, unless the copy was made unconditional, and then it would be difficult to test all the likely combinations that might be found in user environments.

I think this represents a better approach. It also has the advantage of making the container's implementation conform with the Domoticz documentation "as written":

• See Custom menu.

Service definition change

1. Original (single) volumes clause:

   - ./volumes/domoticz:/opt/domoticz/userdata

   becomes a (dual) volumes clause:

   - ./volumes/domoticz/userdata:/opt/domoticz/userdata
   - ./volumes/domoticz/templates:/opt/domoticz/www/templates

   Note the insertion of the userdata folder on the left hand side of the first mapping. This avoids overlapping paths into the persistent store, which can cause its own problems.

Dockerfile changes

1. Formally define the second exposed volume:

   VOLUME /opt/domoticz/www/templates
   

2. Make a copy of the content of the templates folder so it forms part of the image. The destination path (inside the image) is:

   /opt/domoticz/www-templates
   

   Any changes to the source templates folder which come down from "upstream" will always get copied into this folder whenever the image is rebuilt.

docker-entrypoint.sh changes

1. Return the WEBROOT variable to its original location at:

   /opt/domoticz/www
   

2. Withdraw the -wwwroot argument (which implies /opt/domoticz/www as the default).

3. Remove copy of entire www folder to persistent store.

4. Add unconditional copy of /opt/domoticz/www-templates to /opt/domoticz/www/templates.

   There are two mutually-exclusive options:

   • a conditional copy allows users to modify the .example files and have their changes persist - at the price of upstream changes never getting propagated; and

   • an unconditional copy which guarantees any upstream changes to .example files will always get propagated - at the price of losing any user edits to the .example files,

   At this stage, the unconditional copy seemed appropriate.

Explanation

Taken together, it works like this:

1. Each time the image is built, a copy is made of the web templates.

2. When the container starts, the external/internal mkdir and the mount operations triggered by the second volumes: clause cause www/templates to become a "mount point", thereby making its original contents invisible, both inside and outside of the container.

3. When docker-entrypoint.sh runs, it copies the saved copy of the templates back into the mount point, meaning the templates are now available both inside and outside the container. The copy does not affect anything the user does within the templates folder in the persistent store (eg creating .html files).