Remove obsolete files from Eto - Android.csproj.
Initial checkin of Eto.Pcl.csproj. This builds Eto as a Portable Class Library. Eto builds but does not work yet. The reflection API's in particular, need to be moved to the PCL pattern. There are two build symbols at play:

PCL: Non-portable code that cannot not be made portable is disabled via #if !PCL
WINRT: Code that is not currently portable but which can be made portable is marked with this symbol. Once the code has been made portable, it should be marked with #if PCL, or just enabled everywhere (if Eto itself is upgraded to .net 4.5).
Portable class library fixes for Eto.dll. Eliminate some WINRT symbol usages by implementing the appropriate portable code, and use PCL where the code is correct.
More PCL build fixes. Move TypeConverter to namespace MissingTypes to avoid type collisions when compiling downstream assemblies.
Add a parallel set of PCL assemblies for

   Eto.Json, Eto.Test, Eto.Platform.Windows, Eto.Platform.Direct2D and Eto.Test.
These assemblies have the .Pcl suffix and
a) They depend on .net 4.5.
b) They reference Eto.Pcl.dll
c) Each will eventually (soon!) replace the corresponding non-PCL project.
d) Use the PCL #define to disable non-PCL code such as Xaml.

This allows the PCL libraries to be fully built and tested in parallel to the regular libraries until they are ready for production.
More PCL fixes. At this point, Eto.Test.Winforms builds and partially runs, provided PropertyBinding.EnsureProperty is modified to do nothing rather than return an unhandled exception in PCL.