Switch from system() to QProcess

[pinotree]

Using bare system() like this is not exactly safe:

• system() spawns a shell, which is not needed in this case
• arguments are not properly escaped/quoted, e.g. in case of spaces in paths (see above)
• there is no handling of signals, nor a way to make it async
• checking the result is an annoying task

Thus, just switch to QProcess::execute() instead:

• no shell used
• proper handling of arguments
• the execution is still synchronous, but this change allows to change it later if needed/wanted
• checking the result (which is still not done, and ought to be done actually) is easier

[dragotin]

Thanks for catching that one!