make the enums of QProcess known to the meta object system

This enables users to construct enum values from strings
and provides useful qDebug operators.

Task-number: QTBUG-10777
Change-Id: Ia3592f00d559b980b4875ee8fb5e8ffb4328d464
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>