amp 8.x-1.0-beta2

Changes since 8.x-1.0-beta1:

• Fix duplicate REDIRECT_TIME in amp-pixel.html.twig.
• Merge the contexts and add cache key
• Add ability to add ?warnfix at end of node url and see AMP library related warnings if AMP text formatter was used - Also add new node save option to show node in AMP mode with warnings
• Add site wide debugging setting to see AMP library warning messages in the AMP config settings form
• Pass the EntityManagerInterface instead of the entity manager
• Add Module Architecture Overview section to README
• Add information about component support to README
• Add more discussion about overall approach to README
• Remove stray conflict marker