roccat-tools: init at 5.7.0

I had this package along with libgaminggear laying around since June
2016[1] and basically just did the setup for the ROCCAT device once and
never touched it again since then. However, I got requests from other
users who might need this, so I decided to finally upstream it along
with using the latest versions.

There were a few hardcoded paths to fix, like eg. /etc/xdg and another
one that used /var/lib/roccat, the latter I moved into $XDG_DATA_HOME
instead.

The reason why I put it in os-specific/linux is that the official site
explicitly states that it's for Linux only and I specified the platforms
attribute accordingly.

[1]: https://gist.github.com/aszlig/3a01c0c23254a68c2be4c6df59e26862



Signed-off-by: aszlig <aszlig@nix.build>
Cc: @devhell