Test source now plays and records

-In windows anyway, linux is still not tested

-I didn't think multimedia.py line 310-318 were being called. So having
replaced every single part of the pipe line (and then put them back)
this road block came down to the .link_pads call. It caused the pipe to
freeze.

- I accidently copied plugin.py into the usbsrc last commit, I am
deleting in this commit.