- Avoid internal re-opening of PCM objects when parameters change.
- PCM objects can be opened by card id
- Mixer objects can be openend by card index
(this is not consistent, but ALSA works this way)
- Adjusted and cleaned up documentation.
git-svn-id: svn://svn.code.sf.net/p/pyalsaaudio/code/trunk@26 ec2f30ec-7544-0410-870e-f70ca00c83f0