Load projects from yaml file

load_projects command added.
This command should be initialize project_groups and projects.

usage:
storyboard-db-manage --config-file <config> load_projects <projects_file>

Example file added etc/projects.yaml.sample
Tests added.

Change-Id: Ib5cb32064aa0629c45c3249e08a0ca2281acd8f0
Merge "Load projects from yaml file"