How to install ProFTPd with TLS support on Ubuntu 15.10

FTP is a very insecure protocol because all passwords and all data are transferred in clear text. By using TLS, the whole communication can be encrypted, thus making FTP much more secure. This article explains how to set up ProFTPd with TLS on an Ubuntu 15.10 server, how to add an FTP user and to use FileZilla to connect securely with TLS.