GS2 implementation on Pattern Generator needs to guard against invalid inputs

[mbreiser]

1. GS2 implementation on Pattern Generator needs to guard against invalid inputs
   e.g. range of high/low level should be 0/1
   also update (Eventually) with stretch val.

2. another bug...
   the default frames suggested in ANIMATE frame shifting needs to update w. arena, but does not (always 40x200)
   also, let's make default a G41 arena for now.

3. when we load an existing pattern, do we really need to save it (save button is live)...does it change anything or just pass it through?