Show latest commit hash somewhere on the page

[ricardoboss]

To aid in debugging a problem, it helps to know which commit was used when deploying the frontend. Including it should be trivial:

• the Dockerfile can read the commit sha1 and store it in an env file (for example: VUE_APP_GIT_REF)
• the Vue app can check if the variable is set and display it/include it somewhere in the frontend code (for example as a title attribute on the TRENZ logo, so it shows up when hovering over it)

[ricardoboss]

To make this work, a script might need to access .git from within the docker container during build. To make this possible, this commit needs to be reverted: a0150d9