Revert #3218 and deprecate accessing global paths from Handlebars

[xtian]

In Progress

As discussed in #3218, this PR reverts the addition of the ember-handlebars-caps-lookup feature flag and adds a deprecation warning when global paths are accessed from a Handlebars template.

I'm trying to fix the original inconsistency that was reported in #3098 (between {{Foo}} and {{#each Foo}}) by changing bindings to look up values on the given context before Ember.lookup. That part is incomplete and I'm not really sure what to change to get the rest of those tests to pass. Would love to be pointed in the right direction there.

I'm also not sure if it's possible to add a deprecation notice in the {{#each Foo}} case since the binding doesn't know whether it's being created from a template or not.

cc @ebryn

[xtian]

�Related: #3436

[stefanpenner]

you have upset travis

[ebryn]

@xtian ping re: failing travis build

[mixonic]

#3852 and #4124 are addressing the root cause of this.

Actually, sorry, that is not true. They address the inconsistency, but don't say anything about what can or cannot be accessed from a template.

[ebryn]

@xtian ping again
@mixonic - if @xtian doesn't get back to this soon, could you take over this?

[mixonic]

I think the template level changes here seem reasonable. I'm far less sold on the changes to packages/ember-metal/lib/binding.js. Additional tests need to be added for the deprecation imo and from the test output it looks like there are many tests that should be updated to not reference a global (looots of deprecation notices in that output).

I'll take a fast stab soon if @xtian wants to pass the torch.

[ebryn]

@mixonic Looks like he's MIA, could you take over?