docs(input): `ngModel` uses priority 1
docs(guide/directive): fix typo
refactor($compile): simplify regular expressions

Closes #9637
feat($anchorScroll): add support for scrolling independently of `$location.hash()`

Add an optional argument to `$anchorScroll()` to enable scrolling to an
anchor element different than that related to the current value of
`$location.hash()`. If the argument is omitted, the value of
`$location.hash()` will be used instead.

Closes #4568