fix #31151: crash on add of frame from linked part
Plugin work. Plugin maanger and styles of QML-called screen items
Corrections & updates for plugin manager. Replace style settings as
before this branch.
Initial fix to prevent serveral plugin crashes.
Further work required.
Fix #25292 Fix #25604 Fix #25051
Provide the base window as widget reference to style methods that user
it if one isn't provided, as is the case when drawing QtQuick objects
Merge pull request #1238 from MarcSabatella/31151-frame-part-crash

fix #31151: crash on add of frame from linked part
Merge pull request #1246 from MarkRS-UK/RadicalNewPluginManager

Radical new plugin manager