rose.config: load with optional configurations.
rose.config: use load_with_opts in rest of system.
rose.config: load_with_opts: add `rose edit` test.
rose-meta.conf: document optional configuration.
rose config: add tests.
Merge branch 'master' into 425.rose.config.load_with_opts
rose.config: improve file object detection logic.
rose test-suite app-run: 07-opt: test opts setting.
Merge pull request #454 from matthewrmshin/425.rose.config.load_with_opts

rose.config: load optional configurations