Tooltip for lock icon + starts in unlocked mode
Tooltip wording fix
Syncs locking state of all realm windows
remembers locking state between sessions, separately for each document

https://app.asana.com/0/15028213105325/16105342773907
Fixes for JPs comments
Fix compilation with the Xcode 6 GM

Disables Swift support on OS X for now as 6 doesn't support it and we currently
don't support 6.1
Rewrite the Swift class support in Objective-C

Turns out that you can't use Swift in a framework on iOS 7, so move everything
but the convenience functions in Objective-C and switch to building a static
framework. The remaining Swift code is left in a single file which must be
included directly in the user's application (if they want to use it).

This happens to add support for optional RLMObject properties in Swift.