feat(ngRoute): add method for changing url params

Request Type: feature

How to reproduce: 

Component(s): ngRoute

Impact: medium

Complexity: small

This issue is related to: 

**Detailed Description:**

Add a `$route#update` method for changing the current route
parameters without having to manually build a URL and call `$location#path`.
Useful for apps with a structure involving programmatically moving
between pages on the same route, but with different `:param`
values.

**Other Comments:**


you don't need the `defaults` helper, use `extend({}, this.current.params, newParams)`