Mark classes and methods unavailable for extensions

Created by: felix-dumit

This is mostly relevant to when using cocoapods, as of version 1.1.0 you can no longer have a Podfile with a different subspec for the app target and extensions, i.e:

use_frameworks!

target 'TestApp' do
   pod "Bolts"
end

target 'Today' do
   pod "Bolts/Tasks"
end

[!] The 'Pods-TestApp' target has frameworks with conflicting names: bolts

So the solution is to use pod 'Bolts' for both targets. In order to do that some methods/classes need to be marked as unavailable so the app is compilable.