[Scene Kit] Added samples to public yosemite repo

- Added Scene Kit Session WWDC 2013 to public samples.
- Added Scene Kit Session WWDC 2014 to public samples.
[Scene Kit WWDC 2014] Updated resources

- Updated resources for the sample.
[Scene Kit WWDC 2013] - Removed NuGet packages

- Removed Newtonsoft.Json from the repo, it will redownload
automatically.
[Scene Kit WWDC 2014] - Removed NuGet packages

- Removed Newtonsoft.Json from the repo, it will redownload
automatically.
[Scene Kit WWDC 2013] - Migrated to Unified APIs

- Sample was migrated to Unified APIs 2.0 and all types failures were
fixed.
Merge branch 'master' of github.com:xamarin/mac-samples
[Scene Kit WWDC] - Updated metadata files

- The metadata files now include the Yosemite tag.
Merge branch 'master' of https://github.com/xamarin/mac-samples
[Scene Kit WWDC 2013] - Updated README

- Updated README file.
- Updated Metadata file.
Updated all Mac Samples README files

- We now have a well structured README file for each sample. It helps
having coherence between all the samples and display clear information
on the website.
Updated Mac Samples README files

- Add ` symbol for code text.
- Fixed some wrong markdown.
- Updated incorrect README files.
Updated Mac Samples README files

- Now README titles match the project name.
[Scene Kit WWDC Samples] - Updated to NMath

- We no use NMath instead of Math. This avoid a lot of useless casts.