fix($locale): Allow currency filter to fall back to maxFrac from locale

- Modify default fallback to `NUMBER_FORMATS.PATTERNS[1].maxFrac`

- Remove unnecessary resetting

Closes #10179
fix(ngModelOptions): preserve context of getter/setters

Many thanks to @NevilleS and @jbedard for collaborating with me on a solution to this!

Closes #9394
Closes #9865

BREAKING CHANGE: previously, ngModel invoked getter/setters in the global context.

For example:

```js
<input ng-model="model.value" ng-model-options="{ getterSetter: true }">
```

would previously invoke `model.value()` in the global context.

Now, ngModel invokes `value` with `model` as the context.

It's unlikely that real apps relied on this behavior. If they did they can use `.bind` to explicilty
bind a getter/getter to the global context, or just reference globals normally without `this`.
test($http): parsing headers with multiple values

Closes #9473

Closes #10176
fix ($http): throw error when string URL is provided