* Fix all warnings about non-explicit constructors except for those
   in 3rdparty code.

and make it possible to configure it in the settings.
Split up S60Devices up into a class hierarchy and implement
the Autodetected Windows case and the manually configured
Linux case separately for code clarity. Same with the settings
widgets.
Reviewed-by: con

Some categories do not have icons yet, unfortunately.

  * Use id() for methods returning a string used to represent
    some type of object.
  * Use displayName() for strings that are meant to be user
    visible.
  * Quieten some warnings while touching the files anyway.
  * Move Factories to their products in the plugins where that
    was not done before.

Reviewed-by: dt

Display the error in a label of the preferences page.
Reviewed-by: con