Comment why we need to enable the editability of the Text actor
inside the test suite.
This should clarify commit ea508ea528d61ae478d8bc4c88f54a89304f18e8
Whenever we are sending specially crafted KeyEvents to a ClutterText
we also need to set it editable, since the event handling code depends
on the editability setting.
Instead of changing the unit for ClutterEntry, we add a new
test unit specifically for ClutterText so that we can later tweak
it specifically for the behaviour changes needed to make ClutterText
work better.
