New configfile loader, removed mozwebqa

- `from utils import conf`
    - Supports yamls of arbitrary naming (e.g. `cfme_tests/conf/anyname.yaml == conf.anyname`)
    - Supports local override yamls (`cfme_tests/conf/anyname.local.yaml`)
- mozwebqa fixture has been replaced with duckwebqa
    - The ridiculous name is incentive to get our pages to stop using it.
    - To use, ask for duckwebqa instead of mozwebqa.
    - Existing navigation fixtures have been converted to use duckwebqa
    - There is also a duckwebqa_loggedin fixture, which is module scoped. See it in action in test_navigation_fixtures