Update GameServiceContainer.cs

Added generic overloads for AddService() and GetService().
Simpler and cleaner to use, and with the generic GetService() there's also need to cast/unbox from object.
Add FileHelpers.ResolveRelativePath and use it.

Fixes #2577
Initial check in of the Guide issue #2584

Resolved issue of reference to PlayerIndex in MG XNA over MS XNA but requires two externs

ProtoBuild is not putting the second alias on the associated MG lib
Added support for page specific URLs.
Merge pull request #2593 from SickheadGames/docs2

Page URLs for Documentation
Simplify and fix for WINRT
Updated ProtoBuild to the updated version and rebuilt project.

Tested successfully, Guide now restored to WP project
Updated alias to include "gobal".  Seems the cleanest way to avoid changing other code.
Couldn't see an easy way in the protobuild config to have a separate reference map for just one platform.
This pattern also ensure other future splits can follow a working pattern
Implemented GraphicsAdapter.IsWideScreen
Added GraphicsAdapter.IsWideScreen documentation
Merge pull request #2597 from thefiddler/widescreenfix

Implemented GraphicsAdapter.IsWideScreen
Merge pull request #2585 from danzel/combine-uri-file

Add FileHelpers.ResolveRelativePath and use it.
Merge pull request #2596 from DDReaper/Return_Guide_To_WindowsPhone

Return guide to windows phone
Update GamerServiceContainer.cs - removed exception

Ok, so we return null instead of throwing the exception... and in order to achieve this T must be a reference type.
Merge pull request #2566 from TommasoScalici/develop

Update GameServiceContainer.cs
Update to dev release NuGet's

Includes
* New .Net package
* Added Android/iOS/MacOS experimental project templates to main MG NuGet
* Added build specific builds to binaries package (Win 8 x86/x64/ARM/Any) (WinGL x86/x64/Any)

Published as of commit https://github.com/mono/MonoGame/commit/e58c2cef02226c08bb3a132fb90282061914ce29
Merge pull request #2601 from DDReaper/develop_322_NuGet_Update

Update to dev release NuGet's
Do not generate any networking projects for Angle. Angle is just for testing GLES and does not need networking.

Fixes #2592
Merge pull request #2603 from danzel/no-angle-net

Do not generate any networking projects for Angle.