QtSignalForwarder: use full name QObject::connect

Signed-off-by: Branislav Katreniak <bkatreniak@nuvotechnologies.com>
QtSignalForwarder: add support for context in signal connections

This matches new QObject::connect syntax in qt 5.2

Signed-off-by: Branislav Katreniak <bkatreniak@nuvotechnologies.com>
QtSignalForwarder:delayedCall destroy callback immediately after timeout

Original code destroyed the callback asynchronously when QTimer was
deleted with deleteLater