Updating mac tx to transmit on primary port 0

We don't want to broadcast to PHY mode ports
Adding GET_AVB_INFO 1722.1 command
Removing old avb_status structure
Fixing bug in setting rate using API
Making sure a default sink rate is set
Adding 1722.1 stream format get+set commands
Adding 1722.1 get/set sampling rate commands
Correcting response formats to share same format
Removing PTP derived audio clocks as an option
Adding an internal clock source desriptor
Updating media clock get/set to use correct enum

Was previously using the media clock server's local enum rather than the
AVB control types API
Adding 1722.1 get/set clock source commands
Removing name strings from API

Handled by 1722.1 or the user control layer
Adding 1722.1 start/stop streaming + tidyup
Mass update to new documentation system
Update app with more configuration
Added missing files
Updating and cleaning 1722.1 API and docs
Merge pull request #15 from davelxmos/master

Add more configuration options to demo app
Merge branch 'master' of https://github.com/xcore/sw_avb