Cleaned up IO shit crap. Now switching between a device and original
M-Unit device happens properly.
Mumps crazy left to right evaluation catches me again.

 Q:'+$SY=47  ; GT.M only! didn't work
 Should be:
 Q:'(+$SY+47)
Add test T7, which checks that IO shenanigans happens properly.
Same fix as 2 commits ago. $Q:+$SY=47 doesn't work.
Ignore Eclipse project stuff
T8: Test for 'If IO starts with another device, write to that device as
if it's the pricipal device'