added basic web based messaging server

messaging-app/Dockerfile

messaging-app/app/app.py

messaging-app/app/templates/base.html

messaging-app/app/templates/index.html

messaging-app/app/templates/login.html

messaging-app/app/templates/macros.html

messaging-app/app/templates/register.html

messaging-app/app/templates/send_file.html

messaging-app/app/templates/send_message.html

messaging-app/app/uploads/malicious.sh

messaging-app/docker-compose.yml

messaging-app/malicious.sh

messaging-app/requirements.txt