Re-introduce FormWindowEditor as IEditor used for
Designer. Use SharedTools::WidgetHost directly
for embedding into FormEditorStack, doing the
geometry-changed handling in there as well.
Re-introduce FormEditorFile that delegates dirty handling to the form
window. Change DesignerXmlEditable to be an IEditor that embeds
TextEditable so that the PlainTextEditor can work with it, but delegates
relevant functionality to FormEditorFile.
Centralize all form window creation code that was scattered around
in FormEditorW::createEditor() and have that return a struct Editor
data, which is passed to FormEditorStack.
Update the text editor only on open/createNew/switch away from design
mode.
* Use id() for methods returning a string used to represent
some type of object.
* Use displayName() for strings that are meant to be user
visible.
* Quieten some warnings while touching the files anyway.
* Move Factories to their products in the plugins where that
was not done before.
Reviewed-by: dt
