About info should be visible on any page

[cdeil]

Currently the "About" button is only visible on the maps page.
It would be good if on any page on gamma-sky.net there would be some way to reach this info.
Concretely on this page it's not clear how to find out what this webpage is: http://gamma-sky.net/#/cat/tev/142

@vorugantia - What do you think is the best (or quickest) way to improve this? Copy the "About" button onto that view? Or add a footer there, which just links to the docs, or shows the same popup?

On the desktop I like the buttons, but on my phone they are too large and don't work well as a user interface element. Not sure if we should put emphasis on mobile, just mentioning it. I think most people use it on their desktop / laptop, but I can imagine someone wants to quickly look up some source info on their phone during a presentation, so if it's possible to support, we should.