RFC: Ember 1.13+ Idiomatic Style

I'd like to open a discussion about some things for the future of the library. These changes would likely require a major-version bump.
### Positional Params

Change

``` hbs
{{list-filter list=myUserList partial='list-user' properties='name title description'}}
```

to

``` hbs
{{list-filter "name" "title" "description" list=myUserList partial='list-user'}}
```

It would still be possible to have `[ "id" ]` be the default (just check whether the `positionalParams` are empty). It feels a little weird to me, but I have no strong feelings on the subject.
### Block-Form

Change

``` hbs
{{list-filter list=myUserList partial='list-user' properties='name title description'}}
```

to

``` hbs
{{#list-filter list=myUserList properties='name title description' as |user|}}
{{link-to user.name user}}
{{/list-filter}}
```
### Decompose

There are places in our app where the `` and the `

` can't be next to one another in the DOM. Thus, while I love the "easy-use" version of `{{list-filter}}`, it would be nice to decompose it as something like

``` hbs
{{#list-filter-container list=myUserList as |changeFilter filteredList|}}



Users


{{list-filter-input changeFilter=changeFilter}}


{{#each filteredList as |user|}}

• {{link-to user.name user}}

{{/each}}


{{/list-filter-container}}
```
### Small Things
- change `list=` to `content=` to match `ArrayProxy`, which has influenced many other addons
- extract the filtering logic to a helper, make it easier to override
- use `Ember.get(obj, prop)` instead of `obj.get(prop)` to support bare JS objects

Start by reviewing the existing list-filter component and its current usage; the issue names no files or tests. First scope the proposed API changes, then define completion around an agreed direction for positional parameters, block form, decomposition, and the listed smaller changes.

Written by the indexing model from the issue text.