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
Library search paths are configured on the app project level for the sample apps (c.f. [this section of the project](https://github.com/wmathurin/SalesforceMobileSDK-iOS/blob/unstable/hybrid/SampleApps/AccountEditor/AccountEditor.xcodeproj/project.pbxproj#L564)), and generally shouldn't need further configuration, since they'll look for workspace libraries in the `BUILT_PRODUCTS_DIR` folder.