Unify usage and API of CppCheck class. Allow only one file checked
at a time, instead of list of files. Clients can then handle file
lists more naturally and as they see fit. Also clients have better
knowledge of how checking status should be handled.
The single-threaded CLI checking was only one using the file list.
Other clients were giving files (to list) one file at a time.
Threads must be exited from check cleanly even though it takes small amount of time. Just terminating thread can have unpredictable side-effects (even weird crashes).
The number of threads is now atleast 1.
Added a very simple about dialog with version number and license.
Replaced all CppCheck's with Cppcheck.
Renamed "show more errors" to "show possible false positives" in the menu.
User created application now has to have a name and a path.