spanish updates
Allow standard .net build actions in shared projects

Fixes bug 20024 - Shared Projects only allow Compile and None for
Build actions.
[Core] Register unsupported window phone project
[Shared projects] Avoid adding files twice

When syncronizing the shared files of a shared project, avoid adding
the files twice.

Fixes bug 20025 - Xamarin Studio Shared Project will not build on
Xamarin Studio 5
Merge pull request #559 from fernandolguevara/master

spanish updates