[Echo.Loader] divide canvas URLs by provider;
[Echo.Canvas] add "provider" config parameter; use CORS in case of fastly
update CI and sample configs
[Canvas tests] waiting for all apps are ready
[Loader test] add test for the loader in case of using canvases in fastly provider mode
[Echo Loader, canvases] use proper way to mock CORS requests
Merge branch 'neurostep/fastly-canvas-provider' into rc3.0.20