[General] Update copyright to 2013
[Samples] Fix Toolkit samples to use SharpDX.targets
[Build] Fix compilation errors for WP8
[Build] Fix release notes for 2.5.0
[Samples] Fix WP8 sample using SharpDX.targets
[SharpDX] Fix compilation issues for Net20 target
[Build] Fix build for Windows 8
[Build] Fix path for generated XML documentation
[Toolkit.CompilerTask] Add Bin\Redist\D3D to PATH variable in order to support D3DCompiler_46.dll automatically
[Build] Fix various build issues (WP8, documentation)
[Build] Fix various build issues (WP8, documentation)