* part of DSL 1.0 review
* `destination_path` was always a bit vague (it refers to
Cask-specific, version-specific location under
`/opt/homebrew-cask/Caskroom`)
* here renamed `staged_path` to match upcoming command verb
`brew cask stage`
* rename also intended to reduce confusion when we implement
copying as a configurable alternative to symlinking
* transitional `destination_path` methods to remain while
Casks are converted (this was documented as a part of the
DSL, and used by 39 Casks in main repo)
* unrelated variables containing "stage" recast for clarity
- abstracts out common logic, much code removed
- fixes one bug/inconsistency: some artifacts failed to
"return false" when the target exists in "preflight_checks".
- one trivial functional change: artifact type and quotation marks
added in all user feedback (quotes needed b/c of pathnames
containing spaces)
- this allows us to support casks for things like "dmg in zip" "zip in
tar", etc, etc
- a nested container can be any format that homebrew-cask supports
- the existing container support is now referred to as a Cask's
"primary container"
- use the `nested_container` artifact type to indicate the relative
path to a nested container that you wanted extracted
- multiple layers of nesting should work with multiple nested_container
directives (though this is untested as yet)
- add SpeedDownload as the first cask to use this feature; refs #602
