[BUGFIX] Fix an issue with concatenatedProperties.

This commit fixes an issue with how contactedProperties are applied that
can result in subclasses sharing a reference to the same array, in a
surprising way. As an example, the failing test provided here shows
how two Ember.App subclasses shares were sharing inadvertently
sharing initializers.

Thanks to @kselden and @stefanpenner for code review.
Don't allow registration of undefined factories.

container.register(fullName, undefined) now throws
an Exception. This is obviously much stricter then
the current approach, but an obvious win, as we
can detect obviously exceptional scenarios early.
Add readonly attribute support to textarea helper
Merge pull request #3475 from maginatics/master

Add readonly attribute support to textarea helper
[FEATURE ember-runtime-sortBy] Use Ember.compare inside sortBy
Revert "Merge pull request #3475 from maginatics/master"

This reverts commit 39fa88e3a064f52073483856cbde3b06854f2f6d, reversing
changes made to 8e2f82b49ac797091cd401a5703c23ab085a311b.
Merge pull request #3476 from bradleypriest/compare

[FEATURE ember-runtime-sortBy] Use Ember.compare inside sortBy
Merge pull request #3473 from lukemelia/initializers

Fix an issue with concatenatedProperties.
Merge pull request #3414 from stefanpenner/dont-allow-undefined-container-registrations

Don't allow registration of undefined factories.