Make installer apps retina-ready.

Also fixes the generator note.

Change-Id: Ic9a9a033d74320221563c46611122d0fef216c23
Reviewed-by: Iikka Eklund <iikka.eklund@digia.com>
Reviewed-by: Tim Jenssen <tim.jenssen@digia.com>
remove unused class forward

Change-Id: I51d19bb2dac3ffe84f905bf187d361c04694f72d
Reviewed-by: Karsten Heimrich <karsten.heimrich@digia.com>
prepare script engine to get the gui object later

  - Since we need two different script engines we need to be able to set
    the gui object later

Change-Id: Ie40f8ec3dd84dc4d5b3cf127c3e41ce25ef53b66
Reviewed-by: Karsten Heimrich <karsten.heimrich@digia.com>
Mac: Fix Info.plist for installer

Change-Id: I7a0199c3001395356e96c0ef5a0c5104144b9cb2
Reviewed-by: Tim Jenssen <tim.jenssen@digia.com>
Restart on the wizard needs to cleanup component left-overs

  - use two different script engine instances
    - one which lives from the beginning -> the controlScriptEngine
    - the other one which will be reset if there are some new repositories
      loaded
  - now the core has a pointer to the gui object, but it should only be
    used by the script engine so a QObject type should be enough
  - engines are deleted as QObject children from the PackageManagerCore
  - registered downloaded archives are removed

Change-Id: I60a4a32fb2e409059839ec11b10c57357454f57a
Reviewed-by: Michal Klocek <michal.klocek@digia.com>
Reviewed-by: Karsten Heimrich <karsten.heimrich@digia.com>
Merge remote-tracking branch 'origin/1.4' into 1.5

Change-Id: I2725f9bacbe04240dc3f97062c5ebc50884822c8