Allow overriding the Matomo ID

[KlausIllmayer]

For the deployment on the K8s cluster we like to override the Matomo ID. This will be a an environment variable. The task is to make it easily possible to inject it into the Skosmos environment.

[KlausIllmayer]

The current solution are two plugins (one for vocabs-main:prod and one for vocabs-common:prod) with the matomo javascript and the matomo id inside (unfortunately hard-coded). For this to work I also needed to adapt the gitignore and dockerignore, as these are not allowing plugins in the main code. Activation of the plugins is controlled in the config.ttl

Todos:

• move the matomo id and url to an environment variable
• put the plugins into a dedicated git-repository and integrate them into the deployment workflow

[KlausIllmayer]

Look at the todos in the last comment