Adds remote keys (remoteForeignKey and remoteOtherKey) to BelongsToMany relations (similar to the L5 implementation)
For context see https://skedify.atlassian.net/browse/SKED-3792
Base branch was skedify/laravel-framwork:4.2.19 which was originally based upon laravel/framework:4.2.19, skedify/laravel-framwork:4.2.19 did not have a patch number (like p3792 here) because this wasn't our convention yet.