Instead of just a simple list of "nickname"'s which is kind of like the
signing backend's internal ID for a given certificate, provide some more
context to each key.
This is a slight improvement, not a complete overhaul.
Better enforce them now, so that the work to port doesn't increase over
time
Not a super fan of this for regular applications, but oh well the ship
has sailed
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
