Improve ARender Previewer configuration

Context

Configuring ARender Previewer when it is deployed as a docker image presents some limitations such as:

• unable to override properties define in arender-new.properties
• unable to configure the server part
• unable to override the CSS style

Furthermore, default configuration is not the same for embedded deployment and docker one, whereas it should be!

Request

We want to be able to have a default configuration for ARender Previewer (for both deployment). This will result by having three files in the hmi module (one for hmi, one for css and one for server).

We should be able to override these files in both deployment.
This will be done by the docker entrypoint for docker deployment. The script will look for arender.properties, arender.css and arender-server-custom-vanilla.properties.
For the embedded deployment, we will load -hmi.properties and -server.properties files present in nxserver/config/ARenderConfiguration/.