Catch all exceptions occurring in the Smalltalk stack. JS exceptions are converted to instances of JavaScriptException
Renamed Smalltalk >> asSmalltalkError: to #asSmalltalkException:
There were still traces of smalltalk.send in some places.

In IDE, recompile failed because of selection{Start,End}:? methods.
That leaves a few methods with old code.
The selection{Start,End}:? used nonexistent variable `textArea`.
No one seems to be using them, so I removed them.
IDE them recompiled fine.

In collection hierarchy, there were some `smalltalk.send`s
inside JS inline. I refactored the culprits.

It also revealed not-entirely-right
SequenceableCollection >> indexOf:ifAbsent:
which still does not work for Symbol (it did not before, as well).
Merge pull request #341 from herby/smalltalk-send-cleanup

There were still traces of smalltalk.send in some places.