Rename JSDuck config to standard 'jsduck'

Rename JSDuck config to standard 'jsduck'

* Move configuration to /jsduck.json per standard. This way
  it can be run as plain '$ jsduck' without needing a maintenance
  script or custom Jenkins job. Similar to JSHint, JSCS, Grunt,
  and Gem etc.

* Move --processes=0 from maintenace script into config file.
  This should've been in the config file all along and serves as
  workaround for https://github.com/senchalabs/jsduck/issues/525.

* Use grunt-contrib-copy instead of a symlink for resources.
  For local development a symlink works fine, but for publishing
  from Jenkins to doc.wikimedia.org the /docs/js/ directory needs
  to be standalone. This was previously done with a manual post-build
  step that added an additional rsync, but this logic should be
  in the repository so that the doc entry point can be simplified
  and standardised to 'npm run-script doc' for all projects.

Change-Id: Iaaaac50ee78dd9ff8f24f1ef3a3685ad51cf33b2