following up on #3094
- rename `THE_CASK_LANGUAGE.md` to `CASK_LANGUAGE_REFERENCE.md`
- expand `CASK_LANGUAGE_REFERENCE.md` to more fully specify the Cask DSL
- add sections: "Casks Are Ruby Classes" and "The Cask Language Is Declarative"
- import content from `FAQ.md` to `CASK_LANGUAGE_REFERENCE.md`, create multiple sections
listing all stanzas according to category.
- document which stanzas are permitted multiple times
- add previously undocumented `before_install` and `before_uninstall`
- doc that `Hardware::CPU.is_64_bit?` (and 32-bit) are acceptable in conditionals
- doc that `:target` may contain an absolute path (this works more reliably after #3075)
- doc that `uninstall` is optional in the DSL, but required by the community
- link examples
- standardize mixed language on "stanza" over "field"
- further shrink `CONTRIBUTING.md` by deleting rarely used stanzas
and referencing `CASK_LANGUAGE_REFERENCE.md`
Rationale:
- lengthy CONTRIBUTING.md may itself discourage new Cask authors
- it is doubtful that everyone reads to the end, where there
are important notes about squashing.
CONTRIBUTING.md reduced from 7947 words to 1927 words.
This was accomplished principally by spinning out "details" sections
into a new reference file `doc/THE_CASK_LANGUAGE.md`, but also by
ruthless re-organization, removal of duplication, and trimming of
phrases. Content remains 99% identical, though a few typos were
caught along the way, and a table of contents was added.
Võ Anh Duy