rewrite gulp tasks to npm scripts where possible

[Pomax]

our gulp file's super complex, we need to simplify. Ideally to a situation where there isn't a gulp file at all, and tasks (other than watches) are simple piped command chains.

• give each task its own runner file, with only the requirements and inputs it needs
• find and externalise all webpack configs (we have many)
• map each single gulp talk to an npm script
• map each compound gulp task to a compound npm script

[Pomax]

gulp is gone~