Adopt Update dialogs to the new modal widget experience

[TheOneRing]

The update dialogs are still simple dialogs that are now displayed on the full window size.
We need to evaluate how we can update their appearance for a dialog free approach.

client/src/gui/updater/ocupdater.cpp

Line 417 in 8cbcb2c

ocApp()->gui()->settingsDialog()->addModalWidget(msgBox);

client/src/gui/updater/ocupdater.cpp

Line 56 in 8cbcb2c

ocApp()->gui()->settingsDialog()->addModalWidget(_updateDownloadedDialog);

They are currently displayed as a tiny dialog in the top left corner.

[erikjv]

Current state:

[erikjv]

The message box: