Information pop-up

[jeff-saupe]

Problem: Without any introduction, the icons are not enough intuitive (e.g. joining a meeting).
Suggestion: An information pop up with some explanations would be helpful when visiting the page for the first time.

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This issue is referencing to:

I think the icons are without any kind of tutorial not intuitive enough. Maybe we can add a hint when you visit the page for the first time.

Originally posted by @coderesting in #6 (comment)

[coderesting]

I added tooltips in commit 130fa03. In my opinion that makes it clear what the buttons do.