Composer: Add local repository

Sometimes having repos available via http/git is just too much effort, especially when you have your local VCS all setup for development already.

Those local repos can be added as individual repos on the command line.

$ composer config repositories.local-telephone-international-widget vcs /home/elc/source/drupal-contrib/telephone_international_widget

NB: Order is important in composer.json. The first instance of a project encountered in the list of "repositories" will be used, and this command adds to the end. These will have to be re-ordered manually (unless someone can update this with the command line options needed to change that.