Xamarin component

Hey. Here are some changes relative to the component. Of most importance are the changes in the csproj files for Android which fix parameters that are necessary for component aproval.

I noticed that you didn't included in the merge the patches that I applied for the compilation to be successful, any thoughts on that? This pull request won't apply automatically due to that. I know the patches weren't the cleanest solution, so I hope we can come up with something better.

Arturo