Make DesignModeWidget::showEditor reentrant save by explicitly checking
the current status.

The crash happens only reproducably when debugging creator inside
creator (gdb-7.0-ubuntu!).

Reviewed-by: Lasse Holmstedt

Reviewed-by: kkoehne

Task-number: BAUHAUS-451
Reviewed-by: kkoehne

All files have been renamed from Qml to QDeclarative.
Registration of types is now done in an initializer method.
QmlView/QDeclarativeView doesn't have an execute method any more.
QDeclarativeMetaObject became private API.
QmlMetaProperty / QDeclarativeProperty has now different API.

Moved Qt Designer to open from Design Mode. Also, Design mode is now global,
and created in coreplugin. Other plugins can register themselves to it.

This adds a new "Design" mode that can be used to manipulate qml files
in a visual way. It will only get build if you have the declarativeui
module in Qt.

This is a squashed import from the Bauhaus project. Share & enjoy :)