New examples structure and packaging

The previous examples structure was not working very well. We had to run `sh build.sh build` to build the framework in order to build the examples. This PR moves the structure around and only introduces a single Xcode project per platform/language group, with the appropriate Realm Xcode subproject. So the new examples structure looks like this:

```
examples/
    README.md
    ios/
        objc/
            RealmExamples.xcodeproj
            Encryption/
            Migration/
            REST/
            Simple/
            TableView/
        swift/
            RealmExamples.xcodeproj
            Encryption/
            Migration/
            Simple/
            TableView/
        rubymotion/
            Simple/
    osx/
        objc/
        	RealmExamples.xcodeproj
	        JSONImport/
```

The process to package examples for release is:

1. Install Xcodeproj gem from master (https://github.com/CocoaPods/Xcodeproj)
2. Run `./scripts/package_examples.rb`
3. Move the folders in these locations

Follow these steps and all projects should build. Note that there are 3 `Realm.framework`'s. One for iOS, one for OSX and one for Swift (iOS).

```
ios/
    Realm.framework
    examples/
    	README.md
        objc/
            RealmExamples.xcodeproj
            Encryption/
            Migration/
            REST/
            Simple/
            TableView/
        swift/
        	Realm.framework
        	RealmExamples.xcodeproj
            Encryption/
            Migration/
            Simple/
            TableView/
        rubymotion/
        	Simple/
osx/
    Realm.framework
    examples/
        README.md
        objc/
        	RealmExamples.xcodeproj
	        JSONImport/
LICENSE.txt
browser/
    Realm Browser.app
docs.webloc
plugin/
    RealmPlugin.xcodeproj
    RealmPlugin/
```

@emanuelez let me know if you have any questions since you'll be the one integrating this in Jenkins.
Depends on rake. Should be documented.