feat(): add option to html escape all values

Apply an additional functionaly to an interpolator being responsible for escaping interpolated params or using a sanitation service when working with them.

For the default interpolation service, the usage will be:

```javascript
// config
translationProvider.useSanitizedValues(true);
// scope
$scope.user = {link: '/user', name: '<h1>Big User</h1>'};
```

and

```html
<a href="{user.link}">{user.name}</a>
```

will results into the html

```html
<a href="/user">&lt;h1&gt;Big User&lt;/h1&gt;</a>
```
Merge branch 'canary' into feature/xss-protection

Conflicts:
	src/service/translate.js
feat(): add option to html escape all values

In addition to fe94c1f the internal structure of escaping was replaced with a strategy pattern. That allows different kinds of sanitizing including standard html escaping.
Merge branch 'canary' into feature/xss-protection
chore(): prefer angular utils
chore(): prefer angular utils (fix)
Merge branch 'canary' into feature/xss-protection

Conflicts:
	test/unit/directive/translate.spec.js
docs(): add/introduce documention chapter about security
docs(): add/introduce documention chapter about security (typo)
docs(): add/introduce documention chapter about security (corr)
Merge branch 'canary' into feature/xss-protection
Merge pull request #192 from knalli/feature/xss-protection

feat(): add option to html escape all values