Refactor KeyProperty so that getLabel() returns the translation key

This allows the KeyProperty to behave like all the rest of the PropertyBeans.
The getLabel method was renamed to getTranslationKeyLabel method.
The translated value label (a String) which was previously called description can
now be obtained from a UIIcon with getTranslationValueLabel().
Rename getTranslationKeyLabel to getLabel in PropertyAdapter hierarchy

I realized that in the PropertyAdapter hierarchy there is no need to state
that it is a "key to be translated" as there is
no variable that is storing the "translated value".
Make TabProperty retrieve "layoutFormat" through getName instead of getTooltip
Merge pull request #36 from theworldbright/refactor_key_property

Refactor KeyProperty so that getLabel() method returns the translation key instead of the value