comment
improve criteria `extension` method

casecmp was a bug as a substring could match
create a somewhat better fake `pkg` for tests
use `const_get` in container.from_type

instead of iterating over container list
divide Cask::Container::Naked into explicit types

- Cask::Container::Pkg
- Cask::Container::Ttf
- Cask::Container::Otf

which are autodetected based on filetypes as with other
containers.  Cask::Container::Naked remains available
for explicit use in a container_type stanza.
recast `containers` as `autodetect_containers`

and clarify which container types will not autodetect
rename seven_zip.rb to better match class name
doc updated valid values for container_type
Merge pull request #5614 from rolandwalker/container_refactor

Refactor Cask::Container, explicit vs autodetected container types