We have a new, improved string type coming up in AK (OOM aware, no null
state), and while it's going to use UTF-8, the name UTF8String is a
mouthful - so let's free up the String name by renaming the existing
class.
Making the old one have an annoying name will hopefully also help with
quick adoption :^)
Previously, all keydown KeyEvents were accepted, causing parent widgets
not to receive them. With the addition of shortcut handling to keydown,
shortcuts were not called when the ImageEditor was focused.
Wand Selection tool uses similar logic to the Bucket Tool. Flood filling
and threshold calculations to determine the affected area just in this
case we do not set the pixels of the selected area, instead we use
those pixels to alter the selection mask.
In the future we can probably abstract out the shared flood logic so
both tools can share the code.
