Popup a something when a skill is trained

[Josharias]

I want no know when my skill is finished so that I can queue up another one right away instead of checking all the time.

• Could possibly reuse the nag screen for this purpose?
• I think the event works for this and will get sent to the owning client.

[jdrueckert]

Superseded by https://github.com/Terasology/EventualSkills/issues/17