[ngf] Add libcanberra-using sink.

This involves significantly less latency than the gst-using sink. There is some
low-hanging fruit there that may help latency, but for really simple UI elements
that just want to be heard Right Now, using libcanberra is beneficial as we can
also make use of sample caching, etc.

Done-with: Juho Hämäläinen <juho.hamalainen@oss.tieto.com>
[canberra] Set stream properties specified in the effect on the canberra context.

This hopefully makes volume of canberra-using events be what they should be.
[canberra] Only cache samples once, on the first use.
Merge pull request #14 from rburchell/canberra

libcanberra-using ngfd plugin