RHManagedObject.h & RHManagedObjectContextManager.h: added Apple style d...

Hi Chris,

at our company, RHManagedObject is one of the very few third party libraries we use for iOS development, along with our in-house libraries. Since our in-house libraries are almost completely documented using Apple style documentation, I added the same style of documentation to RHManagedObject.h and RHManagedObjectContextManager.h as well.

I figured this might be a useful pull request since this would automatically update the RHManagedObject documentation on cocoadocs.org (http://cocoadocs.org/docsets/RHManagedObject/0.14/) as well.
I added an additional target to the project which will generate and install the docset. All that's required is installing the latest version of the appledoc binary (https://github.com/tomaz/appledoc/releases) and building the Documentation target. Which results to this:

![screen shot 2014-08-13 at 15 00 02](https://cloud.githubusercontent.com/assets/1990895/3905621/0afa1e08-22ea-11e4-9093-7f46e912e313.png)

![screen shot 2014-08-13 at 15 00 36](https://cloud.githubusercontent.com/assets/1990895/3905622/0afde6c8-22ea-11e4-9f0a-55428b26e246.png)

This was added to your latest commit on 25 Jul 2014 (61ef16a). I also added a fetchAsDictionary method that uses the includeSubentities parameter. Other than that nothing else was changed.
 
Kind regards,
David