When XCA started in 2002, there were no C++ initializers.
Drop explicit initializers from the constructors.
- Fix indentations of section declarators.
- Replace NULL by nullptr when feasible.
- Sort private section: properties first, then methods.
The ImportMulti dialog does not show up if there is only
one item to display, but the item is displayed directly.
The displayed items have a new "Import" button to import
directly from the viewed item.
If XCA is called with certs, crls, keys etc. from the commandline
XCA only displays and optionally imports the item if a default
database is given. Afterwards XCA exits.
