Add Copyright info for OS/Distro icons

[daPhipz]

I know this will be tedious work, but very important as well.
We FOSS folk are sometimes tempted to just use stuff off the internet and to not care about licensing and stuff. I am no exception here xD

But since quickemu gained popularity recently, I think we should think about adding licensing information for the OS/Distro icons we are using.

[philclifford]

@daPhipz I've started some rough notes and links on a branch on my fork (see philclifford#1 ) If anyone wants to hold their nose and take a look, any thoughts / comments more than welcome.