Sync Manager for iOS (work in progress)

Half-way there - but it's probably best to get review/feedback early

- projects dependencies updated
- plugin mostly implemented (in some cases calling methods that don't do anything yet, no events fired in webview yet for sync updates)
- sync down implemented for soql targets (sync status is updated in database but no notifications sent out yet)
- sync up: not started
It seems like we're boxing and unboxing `syncId` all over the place, but I'm not seeing where we need the primitive value very often.  Why not just keep its `NSNumber` representation primarily, and only unbox it into its primitive form where necessary.