Register plugins in docker build

Dockerfile

@@ -38,6 +38,7 @@ RUN npm install --quiet
 WORKDIR /webodm
 RUN npm install --quiet -g webpack && npm install --quiet -g webpack-cli && npm install --quiet && webpack --mode production
 RUN python manage.py collectstatic --noinput
+RUN echo "from app.plugins import register_plugins; register_plugins()" | python manage.py shell
 
 RUN rm /webodm/webodm/secret_key.py