Prepend [Mute] instead of appending

I think that the mute information is more important than the clip name. So I suggest prepending "[Mute]" instead of appending to make it visible even on short clips.

It's in qtractorClip.cpp at QString qtractorClip::clipTitle

I use
sClipTitle = QObject::tr(" [Mute]") + std::move(sClipTitle);
instead of
sClipTitle += QObject::tr(" [Mute]");

Since I have lots of short clips I would even prefer "[M]" instead of "[Mute]".