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
docs(guide/unit-testing): improve unit testing guide

This commit adds to the unit testing guide:

- an explicit section on additional libraries: Karma, Jasmine and
  angular-mocks and link to the docs for those projects too. Explain the
  benefit and use case for each of these libaries
- fully featured test examples and add more documentation
  around them, in particular the controller test
- a clear separation between the section on principles of testing
  and the actual tutorial on writing a test

Closes #8220
doc(injector): adds strictDi documentation to appropriate methods.

Closes #9624
refactor(ngForm): Remove checking event.preventDefault and calling event.returnValue. Related to issue #4557. Worked with @bullwrinkle on this.
docs($location): add examples for some methods

Closes #9754
docs(injector): adds a missing backtick and reformat list.

Closes #10189
fix ($http): throw error when string URL is provided
refactor(*): combine sequence of .push() into one statement

Closes #10192
chore(docs): regroup version selector options into major branches and latest

Before this change we grouped by the  discontinued stable/unstable distinction.

Closes #10053
revert: fix(input): always pass in the model value to `ctrl.$isEmpty`

This commit tried to create consistency by ensuring that `$isEmpty` is not
called on both model and view values but it chose to only use `$modelValue`,
which is not actually correct.

`$isEmpty` is designed to compute whether the `$viewValue` is empty. In
practice this is the only part of the parse/format system that the
directive has control over. We can't rely on the `$modelValue` being in
any particular format since other directives can add in their own formatters
and parsers to completely change this.

(reverted from commit 3e51b84bc19f7e6acc61cb536ddcdbfed307c831)
fix(input[date]): do not use `$isEmpty` to check the model validity
fix(input): set ngTrueValue on required checkbox

Fixes #5164
docs(NgModelController): clarify the value parameter for $isEmpty
fix(linky): encode double quotes when serializing email addresses

Email addresses can (under certain restrictions) include double quote
characters. See http://tools.ietf.org/html/rfc3696#section-3.

For example, `"Jo Bloggs"@abc.com` is a valid email address.

When serializing emails to the `href` attribute of an anchor element,
we must HTML encode these double quote characters. See
http://www.w3.org/TR/html-markup/syntax.html#syntax-attr-double-quoted

This commit does not attempt to improve the functionality (i.e. regex)
that attempts to identify email addresses in a general string.

Closes #8945
Closes #8964
Closes #5946
Closes #10090
Closes #9256
perf(*): use Object.create instead of creating temporary constructors

Closes #10058