fix typo pointed out in https://github.com/emberjs/ember.js/pull/3186#discussion_r5989381
Change docs to mention `setUnknownProperty`

The docs incorrectly said that `unknownProperty` would be called when setting an unknown property.
Smarter linkTo observers

Minor refactor to clean up some linkTo code and fix an inconsistency
whereby `{{linkTo 'elsewhere' this}}` would not automatically update
when the present route's ObjectController's content would change,
since the `this` was only watching the ObjectController, and not its
proxied content object. There was already code that special cased
the resolution of ObjectControllers' content, but it was missing from
the code that sets up the observers; now the same code is shared between
both code paths. Hooray.

Also removed the short-lived and probably unnecessary flag
HELPER_PARAM_LOOKUPS, which was only used for the linkTo,
and enabled linkTo parameters, routeName included, to be
bound paths when unquoted.

Thanks to @abahdanovich for pointing this out.
Added Ember.getProperties

`getProperties` has always existed on `Ember.Object`'s prototype, but
it's been unavailable as a utility function to use on POJO's.
Now `Ember.getProperties` can be used with non `Ember.Object`s, e.g.

    var obj = { foo: 5, bar: 6, baz: 7 };
    Ember.getProperties(obj, 'foo', 'bar'); // => { foo: 5, bar: 6 }
    // equivalent to
    Ember.getProperties(obj, ['foo', 'bar']); // => { foo: 5, bar: 6 }
Update ember-dev to allow for stable builds.
updated ember-testing integration tests to show multiple scenarios
Merge pull request #3212 from toranb/master

updated ember-testing integration tests to show multiple scenarios
Merge pull request #3210 from rjackson/allow_stable_builds

Update ember-dev to allow for stable builds.
Merge pull request #3208 from machty/ember-get-properties

Added Ember.getProperties
Sync router.js
Additional documentation for ember-metal/lib/computed.
Merge pull request #3213 from rjackson/docs_for_computed

Additional documentation for ember-metal/lib/computed.
Merge pull request #3206 from bantic/fix-setUnknownProperty-docs

Change docs to mention `setUnknownProperty`
[fixes #3201] the container (via the resolver) now injects toString on managed objects
Merge pull request #3203 from tricknotes/array-replace

Fix to replace large array
Merge pull request #3209 from stefanpenner/to-string

the container (via the resolver) now injects toString on managed objects
Merge pull request #3193 from machty/better-linkto-observers

Smarter linkTo observers
fix typo

I hope this sounds better now :)
Merge pull request #3215 from sly7-7/patch-2

fix typo
Remove some commented test code.