Extracted a method from the code in the File Manager application which
added actions for activating launch handlers found for the selected
file from the context menu. Applied this method to desktop files
and shortcuts.
Note: made some launch handler related methods in the DirectoryView
static or const which allows passing const DirectoryView& to certain
methods.
(...and ASSERT_NOT_REACHED => VERIFY_NOT_REACHED)
Since all of these checks are done in release builds as well,
let's rename them to VERIFY to prevent confusion, as everyone is
used to assertions being compiled out in release.
We can introduce a new ASSERT macro that is specifically for debug
checks, but I'm doing this wholesale conversion first since we've
accumulated thousands of these already, and it's not immediately
obvious which ones are suitable for ASSERT.
Most of the functions under FileUtils were removed, except those which
dealt with file deletion, as they spawned MessageBoxes for errors, as
such, those functions were written in terms of Core::File::remove.
Previously it was possible to open a link like /home/anon/Desktop/Home,
leading to a folder with the same name. Now it correctly opens its real
path, which is /home/anon
FileManager: Use Core::File::real_path_for to get real path of links
