scide: server status bar - change volume with mouse wheel

Signed-off-by: Tim Blechmann <tim@klingt.org>
scide: server/volume - change volume by specific offset & clip values

Signed-off-by: Tim Blechmann <tim@klingt.org>
Added nil check to prevent errors when updating server meters with fewer in/outputs than the server.
class library: Volume - don't warn if server is not running

the volume makes use of server actions, so the warning is obsolete

Signed-off-by: Tim Blechmann <tim@klingt.org>