[DOC] Improve register/inject documentation

[mixonic]

Improve the rather slim App.register and App.inject documentation. Clear up the initializers section of the application docs.

/cc @ebryn

[stefanpenner]

I'm not sure if this is actually true, ember-data bypasses the normally factory stuff still.

https://github.com/emberjs/data/blob/master/packages/ember-data/lib/system/store.js#L1331-L1337

(this is likely not hard to address though)

[mixonic]

Pretty sure it is still true- with the flag set this branch runs:

ember.js/packages_es6/container/lib/container.js

Lines 701 to 714 in a6cd763

	} else {
	var injections = injectionsFor(container, fullName);
	var factoryInjections = factoryInjectionsFor(container, fullName);
	factoryInjections._toString = container.makeToString(factory, fullName);
	injectedFactory = factory.extend(injections);
	injectedFactory.reopenClass(factoryInjections);
	cache.set(fullName, injectedFactory);
	return injectedFactory;
	}

[stefanpenner]

yes but, https://github.com/emberjs/data/blob/master/packages/ember-data/lib/system/store.js#L1331-L1337 essentially bypasses the container

see: https://github.com/emberjs/data/blob/master/packages/ember-data/lib/system/model/model.js#L1034-L1058

[stefanpenner]

i am wrong, modelFor does the lookupFactory

This is pretty embarrassing because I wrote parts of these code paths.

[mixonic]

lol

[stefanpenner]

i think my maxmem is set to low, causing the LRU to evict important information.