Merge branch '17756-close-btn' into 'master'

New style for close buttons

## What does this MR do?
Adds new style for all `Close` buttons

## What are the relevant issue numbers?
Closes #17756 
## Screenshots (if relevant)   
<img src="/uploads/a1d4cb8c22facb4c170e9cf3b4ae439a/Screen_Shot_2016-05-31_at_2.26.42_PM.png" width="800px">   
<img src="/uploads/d567694d79ec6bd5da0ff2faf8b262b0/Screen_Shot_2016-05-31_at_2.26.09_PM.png" width="800px">   
<img src="/uploads/f5e23d8031427079a334d4e03da466b0/Screen_Shot_2016-05-31_at_2.29.01_PM.png" width="800px">   


cc @dzaporozhets 


See merge request !4388