KDE licence policy update

[Jonathan Riddell]

I'd like to get back to my proposed update of the KDE licence policy

https://community.kde.org/Policies/Licensing_Policy/Draft

I got some comments from Matija Šuklje which I incorporated and it now
includes a handy changelog.

-Note that Qt is LGPL 3 not 2.1
-Code copied from Qt can be GPL 3 as well as GPL 2, check comparible
with your code
-Allow AGPL for web apps
-Encourage AGPL for web apps
-Allow icons to be CC-BY-SA 4
-Allow media files to be CC-BY-SA 4 and no longer allow CC-BY-SA 3
-Note CC-BY-SA 4 is LGPL 3 compatible
-Documentation to be CC-BY-SA 4
-MIT text now one of the more standard variants (modern style with sublicence)
-Links to SPDX licences

The main change is for docs and other non-code files to become
CC-BY-SA 4.  This allows it to be converted to code (it's one-way
compatible with LGPL 3) and allows us to share with other popular
sources such as wikipedia.  CC-BY-SA 4 is also better maintained,
better understood and internationally recognised than the old FDL
licence.

Jonathan