improve 'port occupied' error message`

[rrayst]

The error message

Membrane is configured to open port %d. But this port is alreay in
use by a different program.

can be confusing, as it is also printed when Membrane (the JVM process) is not allowed to open the port (e.g. when running as non-root).

(Solution might be setcap cap_net_bind_service+epi /path/to/java)

[predic8]

Must the user setcap? If this is the case we can change the error message accordingly. Can you give an example?

[rrayst]

• markdown on membrane-api.io
• change error message, if port<1024 "or maybe you lack permissions to open the port" + link