1.0.10: Added (undocumented) support for 'file[]' input type

- Added new expectedInput type, 'file[]'

- Enables devs to specify that (API and UI) clients should supply a
  sequence of 0 or more files. The UI currently renders this as a
  <input type="file" multiple />

- Added a new template expression function, 'toDir'

  - Only accepts a 'file[]'-like input

  - Copies each file in file[] into a single directory in the working
    directory and returns a path to that directory

  - Enables user's scripts to receive all files in file[] as a path that
    their application can search through

- Using a file[] input in a template expression (e.g. '${inputs.someFileArray}'
  automatically coerces the file array such that each file in the array
  is copied into a single directory.

  - This is effectively sugar for '${toDir(inputs.someFileArray)}'

  - This, along with 'toDir' is one of the few ways to use the file[]
    input type at the moment.

- This feature is currently undocumented due to time constraints and
  missing/buggy features (job copying + defaults do not work with file[],
  for example)