Added fileoembed annotation

Squashed commit of the following:

commit fb2fa44c33a3c1da824afa7613a03ca2d5aa4d5a
Author: Thomas Westfeld <westfeld@mac.com>
Date:   Sat Mar 16 14:48:27 2013 +0100

    Added test cases for FileOembedAnnotations

    * Finished implementation of ADNFileOembedAnnotationTests
    * Added tests to ensure the correct output
    * TODO: write the parser part, too

commit 16b1f505ae7f620039e991ee87a93092eb256e73
Author: Thomas Westfeld <westfeld@mac.com>
Date:   Sat Mar 16 12:17:56 2013 +0100

    adapted GeolocationTests to new category with helper methods

commit de1e3a60eca8ab93cafe1bce7e8fa8bc0b59ff1f
Author: Thomas Westfeld <westfeld@mac.com>
Date:   Sat Mar 16 12:15:18 2013 +0100

    refactored ADNModelTests helper methods into category

    the helper methods for recursive object comparison were refactored from
    ADNModelTests into its own category on SenTestCase. This facilitates to
    test more special models like annotations were additional functionality
    need testing.

commit d635abe8385a24cb1ce1eb8b80506b670cd71403
Author: Thomas Westfeld <westfeld@mac.com>
Date:   Fri Mar 15 22:54:08 2013 +0100

    added unit tests for geolocation annotation

    unit testing of ADNGeolocation
    * round trip to JSON and back
    * conversion to CLLocation object
    * creation from CLLocation object
    * setting attributes from CLLocation object on a existing ADNGeolocation object

commit c72240d7966658e47f0eb5ad8f9c788eaa2777ca
Author: Thomas Westfeld <westfeld@mac.com>
Date:   Fri Mar 15 21:39:10 2013 +0100

    added FileOembedAnnotation mock data

commit 97973c26ae06fa28e86faed5842cc10bb6f2fa61
Author: Thomas Westfeld <westfeld@mac.com>
Date:   Mon Mar 11 22:02:35 2013 +0100

    JSON serialization seems to start working

commit c02eaba60f781987d4416db755cd14877a59b7ee
Author: Thomas Westfeld <westfeld@mac.com>
Date:   Mon Mar 11 20:50:19 2013 +0100

    started file oembed annotation subclass
supporting client image methods on the mac

included preprocessor macros to distinguish between UIImage-based
methods on iOS and NSImage-based methods on Mac OS X.
Merge pull request #22 from westfeld/add_mac_image_handlers

Add mac image handlers