Adding support for Bower updates

This PR enables Bower package updates through the right-click menu in Solution Explorer. The menu item is only visible when clicking on folders called `bower_components` or direct children of it.

![bower integration](https://f.cloud.github.com/assets/1258877/2211223/0ddf272e-99a3-11e3-959c-1e6f8cfe2aef.png)