Add addition toolbar features needed by settings

This includes:
- Support for custom views for MenuItems
- A performClick() on MenuItems for testing
- A NavButtonStyle for changing the back button to a close button
- Reversing the order MenuItems are displayed in
- More getters for properties of MenuItems

Bug: 140301293
Test: Manually, and Settings' unit tests
Change-Id: Ie5d8323e63a2c7fbb7bbe7f30a388f0379753720
14 files changed