QMetaProperty should have QPropertyInfo (similar to QClassInfo)

Hi,

In order to make applications aware of its object's structures, Qt should add a Q_PROPERTYINFO macro, so that it could be possible to add user-specific meta info to a property.

For instance:

Q_PROPERTY(QString firstName READ firstName WRITE setFirstName USER true)
Q_PROPERTYINFO("firstName", "title", "First Name")
Q_PROPERTYINFO("firstName", "description", "Contact's first name.")
Q_PROPERTYINFO("firstName", "custom", "123456789")