icons loaded, LargeIcon added to tooltip, removed TODO comments

# Preface
Here is just large icons for tooltips. Also I've added `{Binding Path=LargeIcon}` in tooltip and removed `TODO` comments about trying out loading icons.
And, as usual...

# Before
![image](https://cloud.githubusercontent.com/assets/8158404/4136634/e5ee907a-337f-11e4-97dc-e8de59444a62.png)

# After
![image](https://cloud.githubusercontent.com/assets/8158404/4136608/933a2614-337f-11e4-852c-27b6e7feb94c.png)

# Reviewers
@Benglin, please take a look.