ensure all public API's of the container are correctly normalized and validated.

Also ensure internal usages are not validated nor re-normalized.
Use imported handlebars before global Handlebars

Prioritizing the global Handlebars causes problems in environments with multiple versions of Handlebars. One should be able to import a desired version.
adds more tests

Conflicts:
	packages/container/tests/container_test.js
Merge pull request #3885 from stefanpenner/tighten-up-container

ensure all public API's of the container are correctly normalized and va...
[beta] Reintroducing nice unhandled action error

I'd removed a similar assertion message in 160a41cf4b because
it wasn't totally correct, but this version
correctly mentions that the error could have
originated from a bubbling controller action.
Merge pull request #3910 from aaronshaf/patch-1

Prioritize imported Handlebars over global Handlebars