Milestones empty state

What does this MR do?

Adds milestone empty state to project, group and dashboard.

Are there points in the code the reviewer needs to double check?

Why was this MR needed?

Screenshots (if relevant)

Screen_Shot_2016-11-07_at_22.27.37

Screen_Shot_2016-11-07_at_22.27.02

Screen_Shot_2016-11-07_at_22.31.39

Screen_Shot_2016-11-07_at_22.32.10

Screen_Shot_2016-11-07_at_22.54.05

Does this MR meet the acceptance criteria?

What are the relevant issue numbers?

Closes #20853 (moved)

Closes #20838 (moved)