Undo of accidental debug info commit

Undo of all changes to Euterpea.IO.MUI.Widget from commit:
f2f8352d1ba81bd536929425a1d93f747744610f
titled "more HSoM changes" by Paul Hudak
Updates to MUI strictness issue

This new approach is cleaner and should provide better performance.
Now, any value that is init-ed will be seq-ed.  Ideally, this should be
deepseq, but in an effort to not change the types, it is just seq.