Set default run options

[nitomartinez]

This sets the default run options. That is run:

Jamulus -s -n

if no options are defined.

This should reduce the complexity ;-)

[grundic]

Could you please update README as well and remove parameters from there and notice they are not required for starting container?
Thank you.

[grundic]

The port can be specified from command line. I think it's better to be explicit and expose it from command line.

[wapolinar]

The docker documentation states:

The EXPOSE instruction does not actually publish the port. It functions as a type of documentation between the person who builds the image and the person who runs the container, about which ports are intended to be published.

So maybe EXPOSE would make sense, then?

[marians]

Having the EXPOSE line here makes it easier to discover which port will be used externally. A good reason to have it here IMO.

[nitomartinez]

Updated README.md