Make containers renamable from .env file

Restored the 'dbHost' variable and renamed the container names to end in '_CONT_NAME' rather than '_HOST'. Also added a note in the '.env' file that the dbHost and DB_CONT_NAME variables must match if you want to use the renamed DB container.

Looks like theres a bug with nested varibles for my docker-compose. Avoiding it by dropping the SERVICE_PREFIX variable.

Added a rename command to the Makefile that regenerates the docker-compose files and the nginx.conf file to enable changing the names of the containers.

This solves old dependency issues

We don't need that anymore, because the chunked uploader sends only small chunks

- this fixes the download of react-image-lightbox and react-pig

Optimize Frontend Docker Image

Add variable to .env to change db host

added comment about removing 'db' container if using your own db server.