A ClutterText can be put in "password mode" by setting the
text as "invisible": every character inside the Text actor's
contents will be replaced when building the Pango layout with
a specific Unicode character.
The Unicode character is set to '*' by default, but the user
can be changed using the provided API.
The TidyText actor is meant as a replacement for both ClutterLabel
and ClutterText.
Any text-displaying and editing actor should derive from ClutterText
and implement the various visual cues to differentiate the editable
from the non-editable state. Those visual cues usually belong to
a high-level toolkit, especially if themeing is involved.
