updated machine conf

- Added opkg management
- Added UBI filesystem configurations
- Limit file system creation to .tar.bz2 and .ubi
Added multimedia tests

- Added gateworks-test recipe which includes:
  - playVideo
  - test_video
  - test_audio
Added two image recipes

- Added gateworks-image-minimal.bb
- Added gateworks-image-test.bb which includes gateworks-test