#152: renamed #extra_repos to #extra_repositories field of BuildList
Merge pull request #27 from abf/abf-doc:152-rename-extra_repos-field
 [refs #152] Rename #extra_repos field of BuildList to #extra_repositories
Updated docs for "Assembly of packages"
Merge pull request #28 from abf/abf-doc:update-assembly-of-packages
 Update docs of "Assembly of packages"