KPropertiesDialog: Split single command entry box into separate exec and args
The desktop entry "Exec" states: "A command line consists of an executable program optionally followed by one or more arguments."
By having a single entry "command" encourages users to write shell commands like "FOO=123 someApp" rather than a legal "/bin/env FOO=123 someApp". This happens to work for things launched by KIO but it is not universal and leads to breakages in cross desktop code.
This patch adopts the pattern used in kdevelop/hotspot/tools where we explicitly ask for executable and arguments.
A similar patch has been made for kmenuedit