Plugincreator

Bring plugin creator load and save dialogs into line with corresponding score dialogs.

This means that 

1) the plugin creator will only save files named with a certain number of filename extensions, in this case only ".qml"
2) the plugin file dialog shows the name of the file, not the full path, in the title bar
I don't get this line. p is a QmlPlugin and don't have a close slot right?