Introducing ShortcutManager

What's supported:
- Most APIs are implemented, except for SM.updateShortcuts(),
the icon APIs in LA, and LA.startShortcut().
- Persisting information, except for icons
- Throttling

In addition, now PersistableBundle has a public copy
constructor from a Bundle. (Do we want to @hide it?)

TODOs:
- Add icon support
- Implement missing APIs
- Listen to PACKAGE_* broadcasts and do clean-up
- Support multi-launcher apps (pinned shortcuts per launcher)
- Dev option to reset throttling
- Load throttling config from Settings
- Backup & restore
- Figure out LauncherApps permissions (BIND_APPWIDGETS??)
- Other minor TODOs in the code
- Better javadoc

Note: This requires Idf2f9ae816e1f3d822a6286a4cf738c14e29a45e

Bug 27325877

Change-Id: Ia5aa555a4759df5f79a859338f1dc5e624cd0e35