Provides a new angular-based path selector widget.

The previous path selector widget was entirely constructed through
jQuery and lacked features that would be needed for use in other areas.
Further, the old path selector provided a reliance on SCSS and provided
complex integrations with newer UI code to use. This provides a simplified
angular directive for generating a path selector and allows option
customization through the directive interface. The systems and systems
bulk environment selection pages have been updated to use this new directive.