* Remove the ImplicitDefaultAction intelligence, so ToggleActionMenu is
not more than a KActionMenu with setDefaultAction().
* Instead, reset the default action when it gets removed from the menu().
This is done by filtering QActionEvent from menu().
* Add an autotest for ToggleActionMenu.
This replaces prior efforts to fix problems in ToggleActionMenu
in !245 and !254, following the discussion on the virtual meeting
at 2021-02-26.
6b26a2b4b and 1786e6c99 have already ported PageView and
AnnotationActionHandler to the simplified interface.
Source files are no longer separated by UI and non-UI and similar,
but only by their build target.
* ui/ -> part/
* Move all source files from conf/ to part/
* Keep config skeleton definitions in conf/, needed for the mobile target too
* Move editdrawingtooldialogtest.h from conf/autotests/ to autotests/
* ui/data/icons/ -> icons/
* Move /part.cpp, /part.rc and similar files to part/
* Adapt include paths in source files
* Adapt CMakeLists.txt files (in / and in subdirectories)
* Adapt /Messages.sh
