[WIP] Universal App support.

[jlaanstra]

This PR adds Universal App support to RxUI 6.x.

Changes

• Switch from Profile78 to Profile259. Profile259 is the new portable profile that should be used for future development. It includes Universal App support. The difference between these profiles is that WCF support is removed from the latter. To switch to this profile I needed to untick Xamarin.iOS and Android, since Xamarin does not yet support this profile in the UI. Manual references work fine.
• Change all .WinRT projects to include Windows Phone 8.1 support.

Some things that need to be done

• Xamarin currently does not support Profile259. We have to wait for them to release this, but for now a manual reference just works fine. It seems the latest Xamarin for Visual Studio Alpha release has support for the new profiles.
• Wait for an Rx.NET update. For now a manual reference of the winrt files works fine. Add Windows Universal support dotnet/reactive#4 and Profile78 => Profile259, which is the same profile without WCF dotnet/reactive#10
• The Events project for WinRT needs to be split up into separate project for WP81 and Win81.
• Splat needs to switch to Profile259 Switch Splat to Profile259. splat#55.
• Add new assemblies for Windows Phone 8.1 Silverlight.

[anaisbetts]

@jlaanstra I don't think we need to switch Splat to Profile259, since its PCLs are only used to compile other PCLs (i.e. Splat.dll doesn't depend on Splat.Portable.dll, it doesn't exist):

(ignore visual glitching on loading GIFs, lolWinRT)

The big thing we need to wait on is the Rx stuff, I've got a PR open for that so we can track the new release

[jlaanstra]

@jlaanstra I don't think we need to switch Splat to Profile259, since its PCLs are only used to compile other PCLs

Other PCLs also need to switch to Profile259 such as this PR does. To be able to still reference Splat from the PCL Splat also needs to be at Profile259.

A PR for Splat is on the way :)

[jlaanstra]

Reactive Extensions for .NET have been updated but their PCL is not in the folder portable-win8+net45+wp8+wpa81 which means that NuGet will not automatically reference it in our PCL.

I have opened an issue at dotnet/reactive#8

[jlaanstra]

I will submit a new PR with updates to the sample apps and remove that from this PR.

[anaisbetts]

Add new assemblies for Windows Phone 8.1 Silverlight.

I'm not sure we need to do that, unless we're using new WP8.1 Silverlight APIs, no? The 8.0 build should be fine

[anaisbetts]

@jlaanstra I'm feelin pretty good about this PR, you?

[anaisbetts]

/cc #589 who is waiting on this

[jlaanstra]

I'm not sure we need to do that, unless we're using new WP8.1 Silverlight APIs, no? The 8.0 build should be fine

Yep, I think is true. Usually they updated the System.Windows.Interactivity assembly to a new version which could cause trouble, but it seems they did not do that this time.

[jlaanstra]

@jlaanstra I'm feelin pretty good about this PR, you?

Me too, but still waiting fior an updated Rx.NET release to include Profile259.

[anaisbetts]

Thanks @jlaanstra!