Extract the methods to work with a choice list in a textarea to TextareaStringListUtility.
Write a test form TextareaStringListUtility.
Avoid NPE in TextareaStringListUtility.
refs #5 wrote a test for TextareaChoiceListProvider.
refs #5 Added tests for GlobalTextareaChoiceListProvider
avoid NPE in GlobalTextareaChoiceListProvider.setChoiceListEntryList.
make runnable with Jenkins 1.466.

the usage of Behaviour object seems to be changed between 1.466 and 1.480.
1.466: Behaviour.register
1.480: Behaviour.specify