Make MussaWindow UI objects pointers

Make MussaWindow UI objects pointers
It appears to me that Qt seems to like UI widgets that are attached to
it to be pointers as it'll sometimes handle freeing said pointer, which is
bad when its a statically allocated member of a class.

So this patch tries to make most of the UI objects associated with
MussaWindow pointers (I had to convert some elements of the
SequenceBrowserWidget as MussaWindow was storing references to them.)