Breaking changes to shared folder API

Explanation of breaking changes: https://blogs.dropbox.com/developers/2016/02/more-breaking-changes-to-beta-sharing-endpoints/

Backwards-incompatible changes!

• /check_job_status groups errors by routes.
• Shared Folder ID format has changed to match API v1.

Backwards-compatible changes:

• ID is now a required field in Metadata.
• Added path_display to Metadata.
• /sharing/list_mountable_folders[/continue]
• Set max length on names and e-mails.
• Added direct_only flag to /sharing/list_shared_links