Community Custom Field Definitions for files

This PR adds a new custom field definition type on Community profiles (public) to support files:

Examples:

// community profile
customFields: [
  {
    [timestampKey]: {
      type: 'file',
      fileType: 'document', // document|video|audio|photo
      label: 'Registration Forms',
      description: 'Please upload your registration form',
      multiple: false,
      visibleBy: 'admin',
      order: 100
    }
  }
]