Fix folding default in script editor for conditionals, loops, case-of

[marceltaeumel]

The left-most-inner-most heuristc works fine to compute the default folding level. However, for some messages, the editor should unfold again:

• ifTrue:
• ifFalse:
• ifTrue:ifFalse:
• whileTrue:
• whileFalse:
• caseOf:otherwise: