Update mcf implementation

- Remove layer name dependency on git repo name.
- Extract collection name from layer and use for setting BBFILE_PRIORITY
  in bblayers.con file
- Make layer name the same as the root directory for the layer.
- Update documentation

Open-webOS-DCO-1.0-Signed-off-by: Iyad Qumei <iyad.qumei@palm.com>