Add a --client-name option to samplv1_jack

[asmuth]

Hey Rui,

first of all thank you for all the brilliant open source software. I very much enjoyed using samplv1 and drumkitv1 on the last weekend.

Attached is a pull request that adds a new option called --client-name to the samplv1_jack program. This option is useful to me as it allows me to start multiple instances of samplv1 and automatically connect them up to other programs using the jack_connect tool. I tried to make the change fit in with the style of the project, but I am not quite sure about the capitalization and naming convention for members.

all the best

[rncbc]

looks good, thanks
later I'll get to adapt to all the others v1s, if you don't mind.
cheers