Add real CLI to the application

[Alex-Vasile]

Current "CLI" implementation does not accept user argument from the command line, they must be hardcoded and recompiled.

Came up from https://github.com/martin-marek/hdr-plus-swift/issues/54

Tasks:

• [ ] Change no-gui build to act as real CLI
• [ ] See if the CLI functionality can be packaged into the .app