GitLab

- volume calibration and THD test case work tuned.
- 59 unit tests pass
- local audio playback / recording works : uses tinyalsa
- host to device ptorocol in host side implemented / tested (with loopback)
- device side recording / playback works for test cases / test_io.xml
- python processing baseline added.
- spectrum algorithm implementated: calculate Transfer Function of device
  over host and check if amplitudes are within margain. Needs parameter tuning
- spectrum test needs some improvements due to the non-flat response from
  ref microphone.
- build is enabled only for linux host except the client code

Change-Id: I8453ac72b6fce7ddbfee7e2cc05207f09f2b3d88