Initialize push notifications.
Update to push features.
Add ExtendSession to MojioClient.
Remove migration related attributes.
Update subscriptions definition.
Merge branch 'master' into push

Conflicts:
	Src/Mojio.Client/MojioClient.Signal.cs
Rename subscription notify to channel.
Merge branch 'push' into develop

Conflicts:
	Src/Mojio/App.cs
	Src/Mojio/Counter.cs
	Src/Mojio/Invoice.cs
	Src/Mojio/Mojio.cs
	Src/Mojio/Product.cs
	Src/Mojio/Storage.cs
	Src/Mojio/Token.cs
	Src/Mojio/Trip.cs
	Src/Mojio/User.cs