Exception>>signalIn: uses context rather than messageText as debugger title

[emdonahue]

Evaluating Exception>>signal in a playground:

Exception signal

Correctly opens a debugger with the title "Exception," which is the defaultDescription of Exception.

Evaluating instead:

Exception signalIn: thisContext

Incorrectly opens a debugger with the title "UndefinedObject>>DoIt," which is the name of the context rather than the Exception's description.

This behavior hides the actual Exception message when the debugger is opened in favor of the less useful context.

It is caused by StDebuggerActionModel>>statusStringForContext, which returns self contextPredicate printDescription rather than self exception defaultDescription. These should be swapped.