Prefer to use normalised signal/slot signatures

Change-Id: I92322fc3404795bea8442b9b849564d5cd39b367
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>
Reviewed-by: Kurt Pattyn <pattyn.kurt@gmail.com>
Use const & for your foreach variables

Change-Id: I6096111284f02f07e1e7864b8795236563d4f6c1
Reviewed-by: Kurt Pattyn <pattyn.kurt@gmail.com>
Make the constructor explicit

Change-Id: I6dcd225de9fee909c4cd1afa70938c2eb7ff819a
Reviewed-by: Kurt Pattyn <pattyn.kurt@gmail.com>