plasma volume applet news and stuff

[Harald Sitter]

ahoy ahoy

# maintainer
As I got unassigned from working on the applet during work hours it
would probably good to have someone else caring for it as I will not
be able to spend time on it moving forward.

# repo
I filed a sysadmin ticket to get plasma-pa (pa=pulseaudio, in line
with plasma-nm) set up as repo in kdereview. I'll push once created.

# licensing
I also added license and copyright statements to all files that didn't
have them, so licensewise the code base should now be good to go.
Essentially everything that remotely resembles a lib is lgpl and
everything else is gpl.

# design
Thomas and I discussed the present user stories during Akademy and
found them somewhat lackluster in more "advanced" uses. Random notes
at the bottom of [1]. The general notion is to keep the applet very
simple by default and put advanced stuff either in the KCM or an
additional advanced applet which one can opt into.

[1] https://community.kde.org/Plasma/Volume

HS