JsonWizard: Add a way to check for existence of a variable

Change-Id: Ia1368334156c33ca270b5cc7d946efcdb7b635a8
Reviewed-by: Daniel Teske <daniel.teske@digia.com>
JsonWizard: Small improvement to error message

Change-Id: I54368d8f7ceba1e43b0834f106edf16e065ad32d
Reviewed-by: Daniel Teske <daniel.teske@digia.com>
QmlDesigner: toolTip -> tooltip and some qsTr fixes

 - "tooltip" is how it is in the component so use this everywhere

Change-Id: Ib8caa26365e50e1f68e04768b051941bbebe146e
Reviewed-by: Thomas Hartmann <Thomas.Hartmann@digia.com>
JsonWizard: Force minimum size to something sensible

Change-Id: I8d6b6b1519dc711710ad4d28148d3e86291bae58
Reviewed-by: Daniel Teske <daniel.teske@digia.com>