Add guideline for creating mutable collections

The alternative syntax is:

```swift
var collection = [Object]()
```

I find this syntax jarring because of the visual combination of the braces and
the parens. It also seems to be taking a too-rigid stance in favor of using
type inference. I believe that the proposed syntax lets you type the object,
and then be explicit about creating an empty array, which will then by typed
appropriately.
> () is typically used to init objects where as types don't use those in most languages

In Swift, Apple did a great job of blurring the line between the two for consistency reasons. We need to take advantage of that, not follow the example of languages that were made years ago by someone in his basement. `Type()` is standard for initialization, regardless of the type.

Nothing looks really strange if you get used to it, as we have previously concluded, and this does apply here as well.

Debunking the 'used by Apple' argument, or any of the other 'arguments' I listed,  doesn't make an argument for the suggested syntax. 

If this just boils down to a taste issue, I'd rather not have a company-wide guideline. I'd be fine with a per-project guideline.